JP2007202227A - Ultrasonic driver - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic driver for reducing a distribution of a vibration speed in a contact region between an oscillator and a movable element in the drive direction without reducing the contact region between the oscillator and the movable element, reducing a slippage between the oscillator and the movable element, and improving the efficiency and lifetime. <P>SOLUTION: An ultrasonic motor is provided with the oscillator 1 having an oscillation element 1-2 for generating an oscillation excited by piezoelectric elements 1-1a, 1-1b, and the movable element 2 contacting the oscillator 1 in a pressed state and driven by the oscillation from the oscillation element 1-2. The oscillation for displacing the oscillator 1 in the normal direction at the contact region between the oscillator 1 and the movable element 2 and the oscillation for displacing the oscillator 1 in the drive direction of the movable element 2 are excited in the oscillator 1. The oscillation excited in the oscillator 1 and displacing the oscillator 1 in the drive direction of the movable element 2 is an oscillation having a combination of at least a n-th order oscillation and a 3n-th order oscillation (n is a natural number). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic drive device that drives a drive target by vibration excited by a vibrator.

Conventionally, many proposals have been made regarding an ultrasonic motor as an ultrasonic driving device that excites vibration in a vibrator by a piezoelectric element and drives a moving body that is in pressure contact with the vibrator in a predetermined direction. For example, an ultrasonic motor has been proposed in which the vibration in the driving direction of the moving body excited by the vibrator is a secondary bending vibration (for example, see Patent Document 1). In addition, an ultrasonic motor has been proposed in which the vibration in the driving direction of the moving body excited by the vibrator is a primary stretching vibration (see, for example, Patent Document 2).
Japanese Patent Laying-Open No. 2004-304877 (page 16, FIG. 1, FIG. 2) Japanese Patent Laid-Open No. 7-337045 (page 8, FIG. 2, FIG. 4)

  However, the conventional ultrasonic motor has the following problems. The vibrator and the moving body are brought into pressure contact with each other, and vibrations that are displaced in the normal direction of the contact portion with the moving body and vibrations that are displaced in the tangential direction of the contact portion with the moving body are excited. This excites elliptical motion at the contact portion of the vibrator with the moving body, and drives the moving body. In this case, the vibrator and the moving body have a finite contact area, but the elliptical motion of the vibrator in the contact area has a distribution in vibration speed in the driving direction of the moving body (there is a difference in vibration speed). .

  For this reason, in the contact area of the vibrator with the moving body, the slider and the moving body slip at a portion where the vibration speed of the vibrator is different from the moving speed of the moving body. Along with the occurrence of this slip, sliding loss and wear of the vibrator and the moving body occur. When the sliding loss is large, the efficiency of the ultrasonic motor is reduced, and when the wear of the vibrator and the moving body is large, the life of the ultrasonic motor is shortened.

  For example, as a method of reducing the vibration velocity distribution (vibration velocity difference) in the contact area between the vibrator and the moving body, it is conceivable to reduce the contact area between the vibrator and the moving body. However, in this method, the contact between the vibrator and the moving body becomes unstable, and there arises a problem that causes generation of abnormal noise and unstable driving in the ultrasonic motor. The details of the conventional ultrasonic motor driving method and problems will be described later in the description section of the present embodiment for comparison with the ultrasonic motor of the present embodiment.

  The object of the present invention is to reduce the vibration velocity distribution in the driving direction in the contact area between the vibrator and the moving body without reducing the contact area between the vibrator and the moving body, thereby reducing the slip between the vibrator and the moving body. It is another object of the present invention to provide an ultrasonic drive device that can achieve high efficiency and long life.

  In order to achieve the above-described object, an ultrasonic drive device according to the present invention is driven by a vibrator whose vibration is excited by an electro-mechanical energy conversion element, and in contact with the vibrator in a pressurized state. The vibrator is excited by vibration that is displaced in a normal direction of a contact point with the movable body and vibration that is displaced in a driving direction of the movable body, and is excited by the vibrator. The vibration displaced in the driving direction of the moving body is a vibration obtained by synthesizing at least an nth order vibration and a 3nth order vibration (where n is a natural number).

  According to the present invention, the vibration displaced in the driving direction of the moving body excited by the vibrator is a vibration obtained by synthesizing at least the nth order vibration and the 3nth order vibration. Accordingly, the vibration speed in the driving direction of the vibrator can be changed to a rectangular wave shape, and the driving direction in the contact area between the vibrator and the moving body can be reduced without reducing the contact area between the vibrator and the moving body. It is possible to reduce the vibration speed distribution (vibration speed difference). As a result, it is possible to reduce slippage between the vibrator and the moving body, and to achieve higher efficiency and longer life of the ultrasonic driving device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a perspective view showing an appearance of an ultrasonic motor as an ultrasonic driving apparatus according to the first embodiment of the present invention. FIG. 2 is a perspective view showing the appearance of the vibrator of the ultrasonic motor.

  1 and 2, the ultrasonic motor includes a vibrator 1 and a moving body 2. The vibrator 1 is formed in a rectangular parallelepiped (rectangular prism) shape, and includes a pair of piezoelectric elements 1-1a and 1-1a, a piezoelectric element 1-1b, a vibrating body 1-2, and a contact portion 1-3. Yes. The moving body 2 is formed in an elongated rectangular parallelepiped (prism) shape, and is made of stainless steel. The vibrator 1 and the moving body 2 are in contact with each other in a pressurized state by a pressing means such as a coil spring (not shown). The moving body 2 is driven in the forward direction and the reverse direction of the x direction, which is the driving direction of the moving body 2, by vibration excited by the vibrator 1.

  The vibrating body 1-2 is configured as a prismatic member made of stainless steel having substantially the same (or the same) cross-sectional shape in the x direction that is the driving direction of the moving body 2. That is, the cross-sectional shape in the plane orthogonal to the x direction of the vibrating body 1-2 is substantially the same (same) at any part of the vibrating body 1-2. Two contact portions 1-3 are integrally formed at a predetermined interval in the longitudinal direction on the upper surface which is a contact surface with the moving body 2 in the vibrating body 1-2. Moreover, the piezoelectric element 1-1a for exciting the expansion-contraction vibration displaced to ax direction to the vibration body 1-2 is being fixed to the both sides | surfaces of the vibration body 1-2 by adhesion | attachment. Further, in order to excite the vibrating body 1-2 on the bottom surface of the vibrating body 1-2, bending vibration that is displaced in the z direction, which is the normal direction of the contact point of the vibrating body 1-2 with the moving body 2, is applied. The piezoelectric element 1-1b is fixed by adhesion.

  The piezoelectric elements 1-1a and 1-1a and the piezoelectric element 1-1b are electro-mechanical energy conversion elements that convert electrical energy (voltage) into mechanical energy (vibration). Electrical energy is supplied to the piezoelectric elements 1-1a and 1-1a and the piezoelectric element 1-1b from a power source (not shown).

  Next, the driving method and operation effect of the ultrasonic motor of the present embodiment having the above configuration will be described in detail based on FIGS. 1 to 7 while comparing with the conventional ultrasonic motor.

  FIG. 3 is a schematic diagram of the piezoelectric element 1-1a that excites stretching vibration. FIG. 4 is a schematic diagram of the piezoelectric element 1-1b that excites bending vibration. FIG. 5 is a schematic diagram showing deformation of secondary bending vibration. FIG. 6 is a schematic diagram showing the deformation of the primary stretching vibration. FIG. 7 is a schematic diagram showing the speed of the combined stretching vibration.

  First, in order to make a comparison with the ultrasonic motor of the present embodiment, a conventional ultrasonic motor driving method and its problems will be described. In the following description of the conventional ultrasonic motor, for the sake of convenience, the drawings and symbols relating to the ultrasonic motor of the present embodiment are used.

  In the conventional ultrasonic motor driving method, for example, the natural frequency of the secondary bending vibration (see FIG. 5) that is displaced in the z direction of the vibrator 1 and the primary expansion and contraction that is displaced in the x direction of the vibrator 1. The natural frequency of the vibration (see FIG. 6) is substantially matched (or matched). An alternating voltage having a phase difference that substantially matches (or matches) the natural frequency of the vibrator 1 is applied to the piezoelectric element 1-1b and the piezoelectric element 1-1a, and the contact portion 1-3 of the vibrator 1 is applied. Excites elliptical motion that draws an elliptical trajectory. The mobile body 2 that is brought into pressure contact with the contact portion 1-3 can be driven in the forward and reverse directions in the x direction.

  However, in this case, the contact portion 1-3 of the vibrator 1 and the moving body 2 have a finite contact region (“contact region” in FIG. 7 (region indicated by an arrow upward from the horizontal line)). In addition, the elliptical motion of the contact portion 1-3 has a sinusoidal distribution in the vibration velocity of the vibrator 1 in the x direction, as shown in “first order (conventional driving method)” in FIG. For this reason, in the contact area between the contact part 1-3 of the vibrator 1 and the moving body 2, the moving speed of the moving body 2 ("moving speed of the moving body" (two-dot chain line) in FIG. 7) is different. As a result, the contact portion 1-3 of the vibrator 1 and the slider 2 slip.

  As described in the above problem column, sliding loss and wear of the contact part 1-3 and the moving body 2 occur as a result of slippage. If the sliding loss is large, the motor efficiency decreases, and if the wear is large, the motor life is shortened. Become. Further, in order to reduce the distribution of the vibration velocity in the x direction that is the driving direction of the moving body 2 of the contact portion 1-3 in the contact area between the contact portion 1-3 and the moving body 2, the contact portion 1-3 and If the contact area of the moving body 2 is reduced, the contact between the two becomes unstable, causing abnormal noise or driving instability.

  The ultrasonic motor according to the present embodiment solves the above-described problems in the prior art by using a driving method described in detail below.

  Next, the driving method and operation effect of the ultrasonic motor according to the present embodiment will be described. The ultrasonic motor driving method of the present embodiment is different from the conventional ultrasonic motor driving method in that in addition to the primary stretching vibration in the x direction which is the driving direction of the moving body 2 with respect to the vibrator 1, 3 This is the point of exciting the next stretching vibration at the same time.

  In this embodiment, in order to excite the primary stretching vibration and the tertiary stretching vibration in the x direction that is the driving direction of the moving body 2 with respect to the vibrator 1, as described above, Piezoelectric elements 1-1a (see FIG. 3) are bonded to both side surfaces. As shown in FIG. 3, the piezoelectric element 1-1a has one surface (A surface) divided into four electrodes (electrode A1, electrode A3, electrode A3, electrode AS), and the other surface (not shown). One electrode is formed over the entire surface (B surface). Bonding of the piezoelectric element 1-1a to the vibrating body 1-2 is performed on the B surface, and the A surface is exposed on the surface.

  The electrical connection between the electrode on the B surface of the piezoelectric element 1-1a and a power source (not shown) is performed by a flexible substrate (not shown) via a vibrating body 1-2 having conductivity (made of stainless steel). Yes. The electrical connection between the electrode on the A surface of the piezoelectric element 1-1a and the power source is also performed by the same flexible substrate. Of the four electrodes on the A surface, the electrode A1 is used to excite the first order stretching vibration, the two electrodes A3 are used to excite the third order stretching vibration, and the electrode AS is the vibrating body 1-2. It is used as a sensor unit that detects the vibration speed. The B side electrode is used as a common ground electrode. Each of the electrodes has the same polarization direction in the thickness direction of the piezoelectric element, as indicated by + in FIG.

  Note that the ultrasonic motor includes a control unit (not shown) that performs arithmetic processing and motor drive control. Based on the vibration speed of the vibrating body 1-2 of the vibrator 1 detected by the electrode AS (sensor part) of the piezoelectric element 1-1a, the control unit calculates the amplitude of the stretching vibration speed of each order in the vibrator 1. To do. In addition, the control unit performs control so that the ratio of the amplitude of the n-th order stretching vibration and the amplitude of the 3n-order stretching vibration in the vibrator 1 substantially matches (or matches) the ratio of 1: 1/3. . These stretching vibrations will be described later.

  Further, in the present embodiment, a secondary bending vibration as shown in FIG. 5 is used as the vibration displaced in the z direction, which is the normal direction of the contact portion of the vibrator 1 with the moving body 2. In order to excite secondary bending vibration with respect to the vibrator 1, the piezoelectric element 1-1b (see FIG. 4) is bonded to the bottom surface of the vibrating body 1-2 as described above. As shown in FIG. 4, the piezoelectric element 1-1b has one surface (C surface) divided into two electrodes, and the other surface (D surface) (not shown) has one electrode over the entire surface. Is formed. Bonding of the piezoelectric element 1-1b to the vibrating body 1-2 is performed on the D surface.

  The electrical connection between the C-plane electrode and D-plane electrode of the piezoelectric element 1-1b and a power source (not shown) is the same as that of the piezoelectric element 1-1a. The polarization direction of the two electrodes on the C plane is opposite to the thickness direction of the piezoelectric element 1-1b as shown by +-in FIG. 4, and the electrode on the D plane is a common ground electrode. The same alternating voltage is applied to the two electrodes on the C plane to excite secondary bending vibrations that are displaced in the z direction as described above.

  As shown in FIG. 5, the contact portion 1-3, which is a contact portion of the vibrator 1 with the moving body 2, has an x-direction which is the driving direction of the moving body 2 in the secondary bending vibration displaced in the z direction. The vibrating body 1-2 is provided so as to have two antinode positions (black circles in the figure) where displacement and speed are extremely small. Thereby, the influence of the secondary bending vibration on the vibration speed in the x direction which is the driving direction of the moving body 2 can be extremely reduced, and the composition of the vibration speed in the x direction due to the stretching vibration of the vibrator 1 can be facilitated. The natural frequency of the vibrator 1 can be lowered.

  In this embodiment, the vibration having the vibration speed in the x direction that is the driving direction of the moving body 2 in the vibrator 1 is large in that the vibration speed in the x direction is large and the vibration can be synthesized most easily. Although vibration is used, it is not limited to stretching vibration. For example, bending vibration can be considered as other than stretching vibration.

  Next, synthesis of vibration in the x direction that is the driving direction of the moving body 2 in the vibrator 1 will be described. For example, the ratio of the amplitude of the primary stretching vibration to the amplitude of the third stretching vibration whose natural frequency is approximately three times (or three times) the primary stretching vibration is 1: 1 / When 3, it is possible to obtain a stretching vibration speed as shown in “first order + third order” in FIG. As a result, in the contact area between the contact portion 1-3 of the vibrator 1 and the moving body 2, the difference between the vibration speed of the vibrator 1 and the moving speed of the moving body 2 can be reduced. As a result, slippage between the contact portion 1-3 of the vibrator 1 and the moving body 2 can be reduced, and high efficiency and long life of the ultrasonic motor can be realized.

  Further, by setting the speed of stretching vibration as shown in “first order + third order + 5th order +...” In FIG. 7, the vibration speed in the x direction that is the driving direction of the moving body 2 in the vibrator 1 is a rectangular wave. It becomes possible to approach. As a result, the difference between the vibration speed of the vibrator 1 and the movement speed of the moving body 2 can be further reduced. Thereby, it is possible to further reduce the sliding between the contact portion 1-3 of the vibrator 1 and the moving body 2.

  In the present embodiment, when the vibration in the x direction that is the driving direction of the moving body 2 in the vibrator 1 is synthesized, only the first and third stretching vibrations are synthesized as described above. The reason is that a greater effect can be obtained with a simple vibrator configuration and a simple circuit configuration.

  In the present embodiment, the case where the lowest order of the stretching vibration in the vibrator 1 is taken as an example is described as an example, but the first order is not limited. Assuming that the lowest order of the stretching vibration is n order, if the vibration is a synthesized vibration of n order + 3n order + 5n order +... + (2m + 1) n order (m and n are natural numbers), the contact portion 1− 3 and the effect of reducing the slip of the moving body 2 is obtained. At this time, in order to make the vibration speed in the x direction, which is the driving direction of the moving body 2, a favorable rectangular wave, the amplitude ratio of the speed of the (2m + 1) n-order stretching vibration to the n-order stretching vibration is 1: 1 /. It is most effective to substantially match (or match) (2m + 1).

  Next, in the stretching vibration displaced in the driving direction of the moving body 2 in the vibrator 1, the natural frequency of the lowest-order n-order stretching vibration and the natural frequency of the 3n-order stretching vibration are approximately integer multiples (or The effect of the points set so as to be an integer multiple) will be described. It has already been described that it is preferable to make the vibration speed in the x direction, which is the driving direction of the moving body 2, close to a rectangular wave, but in order to keep the speed close to a rectangular wave during a certain amount of driving of the ultrasonic motor. It is necessary to synchronize the stretching vibration to be synthesized.

  As a method of synchronizing the stretching vibration to be synthesized, it is desirable to multiply the period of the stretching vibration to be synthesized by substantially an integral multiple (or an integer multiple). In addition, a means for synchronizing the expansion and contraction vibration to be synthesized may be separately provided at regular time intervals. It is desirable to synchronize the contact between the contact portion 1-3 and the moving body 2. This includes the natural frequency of the lowest-order stretching vibration among the stretching vibrations of the vibration velocity in the x direction that is the driving direction of the moving body 2 to be synthesized, and the normal line of the contact point between the vibrator 1 and the moving body 2. It is a simple method to substantially match (or match) the natural frequency of the bending vibration in the z direction that is the direction.

  Next, an effect of the fact that the cross-sectional shape of the vibrating body 1-2 constituting the vibrator 1 is substantially the same (or the same) cross-sectional shape as the driving direction of the moving body 2 will be described. In the vibrator 1, a vibration mode that vibrates in the x direction that is the driving direction of the moving body 2 is an expansion / contraction vibration mode that expands and contracts in the x direction, and a cross-sectional shape in the x direction is substantially the same shape (or the same shape). As a result, the natural frequency of the first-order stretching vibration and the natural frequency of the n-th stretching vibration are in a relationship of approximately n times (approximately integer multiples) (or integer multiples). It can be easily taken.

  As described above, according to the present embodiment, the vibration displaced in the driving direction (x direction) of the moving body 2 excited by the vibrator 1 is a vibration obtained by combining at least the nth order vibration and the 3nth order vibration. And Accordingly, the vibration speed of the vibrator 1 in the driving direction of the moving body 2 can be changed to a rectangular wave shape, and the moving body 2 of the vibrator 1 can be reduced without reducing the contact area between the vibrator 1 and the moving body 2. It is possible to reduce the vibration velocity distribution (vibration velocity difference) in the driving direction in the contact area. Thereby, it is possible to reduce slippage between the vibrator 1 and the moving body 2 and to realize high efficiency and long life of the ultrasonic motor.

  Further, the natural frequency of the nth order vibration displaced in the driving direction of the moving body 2 excited by the vibrator 1 and the natural frequency of the 3nth order vibration are set so as to have a substantially integer multiple relationship. . Thereby, it becomes easy to make the vibration speed of the vibrator 1 in the driving direction of the movable body 2 rectangular, and the above-described effect can be easily obtained.

  Further, when the lowest order of the stretching vibration in the vibrator 1 is set to the first order, the natural frequency of each of the vibrations of a plurality of orders to be synthesized can be minimized, and the above effect can be achieved with a simple vibrator. And a circuit configuration.

  Further, the control unit of the ultrasonic motor substantially matches (or matches) the ratio of the amplitude of the n-order stretching vibration speed and the amplitude of the 3n-order stretching vibration speed in the vibrator 1 to 1: 1/3. Take control. Thereby, the vibration speed in the driving direction of the moving body 2 in the vibrator 1 can be controlled in a favorable rectangular wave shape, and the above effect can be obtained more remarkably.

  Further, by making the vibration displaced in the driving direction of the moving body 2 excited by the vibrator 1 into a stretching vibration in the driving direction of the moving body 2, a large vibration component in the driving direction can be obtained, and the vibration can be synthesized. It becomes easy and the above-mentioned effect can be obtained with an easy configuration.

  Further, by making the cross-sectional shape of the vibrator 1 substantially the same cross-sectional shape in the driving direction of the moving body 2, each natural frequency synthesized by the stretching vibration in the driving direction of the moving body 2 excited by the vibrator 1. Is approximately an integer multiple. Thereby, it is possible to make the vibration speed in the driving direction of the moving body 2 in the vibrator 1 to be a rectangular wave shape with an easy configuration, and the above-described effect can be easily obtained.

  Further, the natural frequency of the vibration displaced in the normal direction (z direction) of the contact point with the moving body 2 excited by the vibrator 1 is changed to the vibration displacement displaced in the driving direction of the moving body 2 excited by the vibrator 1. It is set so as to substantially match the natural frequency of the lowest order vibration. Accordingly, the period of vibration displaced in the normal direction of the contact point with the moving body 2 excited by the vibrator 1 and the period of the rectangular wave-like vibration speed in the driving direction of the moving body 2 in the vibrator 1 are approximately set. It is possible to match. Accordingly, when the vibrator 1 and the moving body 2 are in contact with each other, it becomes easy to make the speed of the vibration displaced in the driving direction of the moving body 2 excited by the vibrator 1 substantially constant, and the above effect is easy. Can be obtained.

  Further, by making the vibration displaced in the normal direction of the contact portion with the moving body 2 excited by the vibrator 1 into a bending vibration, the natural frequency of the vibration displaced in the normal direction can be lowered, and the vibrator The amplitude of 1 is large, and stable contact between the vibrator 1 and the moving body 2 can be obtained. At the same time, with a simple configuration, the period of vibration displaced in the normal direction of the contact point with the moving body 2 excited by the vibrator 1 and the vibration speed of the rectangular wave in the driving direction of the moving body 2 in the vibrator 1 are as follows. It becomes possible to substantially match the period.

[Second Embodiment]
FIG. 8 is a perspective view showing the appearance of the vibrator of the vibrator of the ultrasonic motor as the ultrasonic driving device according to the second embodiment of the present invention, and (a) has a circular cross-sectional shape. The figure which shows a vibrating body, (b) is a figure which shows the vibrating body which has an elliptical cross-sectional shape, (c) is a figure which shows the vibrating body which has a triangular cross-sectional shape.

  8, in the first example of the vibrator of the present embodiment, as shown in FIG. 8A, the vibrator 11-2 of the vibrator 11 is substantially the same in the driving direction of the moving body (not shown) ( Or the same cross-sectional shape. The contact portion 11-3 of the vibrating body 11-2 and the moving body are pressed and contacted in the z direction, which is the normal direction of the contact point with the moving body, by pressurizing means (not shown) such as a leaf spring. .

  Further, in the second example of the vibrator of the present embodiment, as shown in FIG. 8B, the vibrator 21-2 of the vibrator 21 is substantially the same (or the same) in the driving direction of the moving body (not shown). ) Having an elliptical cross-sectional shape. The contact portion 21-3 of the vibrating body 21-2 and the moving body are pressed and contacted in the z direction by a pressing means (not shown) such as a leaf spring.

  Further, in the third example of the vibrator of the present embodiment, as shown in FIG. 8C, the vibrating body 31-2 of the vibrator 31 is substantially the same (or the same) in the driving direction of the moving body (not shown). ) Having a triangular cross-sectional shape. The contact portion 31-3 of the vibrating body 31-2 and the moving body are pressed and contacted in the z direction by a pressing means (not shown) such as a leaf spring.

  Also in the present embodiment, the speed of vibration in the x direction can be made to be a rectangular wave shape by combining the primary stretching vibration in the x direction that is the driving direction of the moving body and the tertiary stretching vibration. Thereby, the effect which can reduce the slip of a vibrator | oscillator and a moving body is acquired similarly to the said 1st Embodiment.

  In this embodiment, the case where the cross-sectional shape in the driving direction of the moving body in the vibrating body is a circle, an ellipse, or a triangle is given as an example, but the present invention is not limited to a specific cross-sectional shape, and other The above effects can be obtained with any cross-sectional shape.

  As described above, according to the present embodiment, similarly to the first embodiment, without reducing the contact area between the vibrator and the moving body, the slip between the vibrator and the moving body is reduced. There are effects such as high efficiency and long life of the ultrasonic motor.

[Third Embodiment]
FIG. 9 is a perspective view showing an appearance of a vibrator of an ultrasonic motor as an ultrasonic driving apparatus according to the third embodiment of the present invention.

  In FIG. 9, the vibrator 41 is formed in an annular shape, and includes a piezoelectric element 41-1, a vibrating body 41-2, and a contact portion 41-3. A piezoelectric element 41-1 is fixed to the bottom surface of the vibrating body 41-2 by adhesion. On the upper surface of the vibrating body 41-2, a large number of protrusion-shaped contact portions 41-3 are formed integrally with the vibrating body 41-2 at predetermined intervals in the circumferential direction. The contact portion 41-3 and the annular moving body (not shown) are pressurized in the z direction, which is the normal direction of the contact portion between the contact portion 41-3 and the moving body, by a wave washer (not shown). Is touching. The piezoelectric element 41-1 of the vibrator 41 and a power source (not shown) are electrically connected by a flexible substrate 43.

  The vibration excited in the vibrator 41 and displaced in the z direction, which is the normal direction of the contact point with the moving body, is a bending vibration out of the plane of the ring. In addition, the vibration that is excited in the vibrator 41 and is displaced in the θ direction (circumferential direction) that is the driving direction of the moving body is the stretching vibration in the θ direction, which is the first stretching vibration, the third stretching vibration, and the fifth order. The stretching vibration is synthesized. The ratio of the natural frequencies of the first-order stretching vibration, the third-order stretching vibration, and the fifth-order stretching vibration in the θ-direction stretching vibration is 1: 3: 5, which is substantially an integer multiple (or integer multiple). It is easy to synchronize stretching vibration.

  In the present embodiment, the driving direction of the moving body that is in pressure contact with the vibrator 41 is the x direction of the orthogonal coordinate system in the first embodiment, whereas the θ direction of the cylindrical coordinate system. (Circumferential direction). Also in the present embodiment, as in the first embodiment, an effect of reducing the slip between the vibrator 41 and the moving body can be obtained.

  As described above, according to the present embodiment, similarly to the first embodiment, without reducing the contact area between the vibrator and the moving body, the slip between the vibrator and the moving body is reduced. There are effects such as high efficiency and long life of the ultrasonic motor.

1 is a perspective view showing an appearance of an ultrasonic motor as an ultrasonic drive device according to a first embodiment of the present invention. It is a perspective view which shows the external appearance of the vibrator | oscillator of the ultrasonic motor of FIG. It is a schematic diagram of a piezoelectric element that excites stretching vibration. It is a schematic diagram of the piezoelectric element which excites bending vibration. It is a schematic diagram which shows a deformation | transformation of a secondary bending vibration. It is a schematic diagram which shows the deformation | transformation of a primary expansion-contraction vibration. It is a schematic diagram which shows the speed | rate of the synthetic | combination stretching vibration. It is a perspective view which shows the external appearance of the vibrating body of the vibrator | oscillator of the ultrasonic motor as an ultrasonic drive device concerning the 2nd Embodiment of this invention, (a) shows the vibrating body which has circular cross-sectional shape. FIG. 4B is a diagram illustrating a vibrating body having an elliptical cross-sectional shape, and FIG. 5C is a diagram illustrating a vibrating body having a triangular cross-sectional shape. It is a perspective view which shows the external appearance of the vibrator | oscillator of the ultrasonic motor as an ultrasonic drive device concerning the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11, 21, 31 Vibrator 1-1a Piezoelectric element (electro-mechanical energy conversion element) which excites stretching vibration
1-1b Piezoelectric element that excites bending vibration (electro-mechanical energy conversion element)
1-2, 11-2, 21-2, 31-2 Vibrating body 1-3, 11-3, 21-3, 31-3 Contact part 2 Moving body A1 Electrode for exciting primary stretching vibration A3 Tertiary That excites the stretching vibration of the electrode AS electrode (detection means)
41 vibrator 41-1 piezoelectric element (electro-mechanical energy conversion element)
41-2 Vibrating body 41-3 Contact part

Claims (9)

A vibrator whose vibration is excited by an electromechanical energy conversion element;
A moving body that is brought into contact with the vibrator in a pressurized state and driven by the vibration;
The vibrator is excited by vibration that is displaced in a normal direction of a contact portion with the moving body and vibration that is displaced in a driving direction of the moving body,
The ultrasonic drive device characterized in that the vibration displaced in the drive direction of the moving body excited by the vibrator is a vibration obtained by synthesizing at least the n-th order vibration and the 3n-order vibration (where n is a natural number). .   The natural frequency of the n-th order vibration displaced in the driving direction of the moving body excited by the vibrator and the natural frequency of the 3n-order vibration are set so as to have a substantially integer multiple relationship. The ultrasonic drive device according to claim 1.   The ultrasonic driving apparatus according to claim 1, wherein the natural number n is 1. 3. Detecting means for detecting a vibration speed of the vibrator;
Based on the vibration speed detected by the detecting means, the vibration amplitude of each order is calculated, and the ratio between the vibration speed amplitude of the n-th vibration and the vibration speed amplitude of the 3n-order vibration is 1: 1/3. Control means for substantially matching
The ultrasonic drive device according to claim 1, further comprising:   5. The ultrasonic drive device according to claim 1, wherein the vibration displaced in the driving direction of the moving body excited by the vibrator is a stretching vibration in the driving direction of the moving body. .   The ultrasonic driving apparatus according to claim 5, wherein the vibrator has substantially the same cross-sectional shape in the driving direction of the moving body.   The natural frequency of the vibration displaced in the normal direction of the contact point with the moving body excited by the vibrator is the lowest order vibration of the vibration displaced in the driving direction of the moving body excited by the vibrator. The ultrasonic driving device according to claim 1, wherein the ultrasonic driving device is set so as to substantially coincide with the natural frequency of the ultrasonic wave.   The ultrasonic driving device according to claim 1, wherein the vibration displaced in the normal direction of the contact portion with the moving body excited by the vibrator is a bending vibration.   The ultrasonic driving apparatus according to claim 1, wherein the driving direction of the moving body is selected from a group including an axial direction of an orthogonal coordinate system and a circumferential direction of a cylindrical coordinate system.

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