JP2008312309A - Vibration type actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibration type actuator capable of allowing a mover fitted to a driver with a screw to move forward by resonating the driver using a driving element provided on a support. <P>SOLUTION: A support 5 supporting the bottom end of a vibration shaft 2 is provided with a plurality of piezoelectric elements 6, 7, 8, 9. Vibration to be imparted to the support 5 is imparted to the vibration shaft 2 via the support 5 by the electrostrictive effect of the piezoelectric elements. The phase of a drive signal to be imparted to the piezoelectric elements is changed, and thus, the driver 3 fixed on the vibration shaft 2 can perform circular motion. A male screw portion 13 is formed on the driver 3, and a female screw portion 14 screwing with the male screw portion 13 is formed on the internal circumferential surface of a center hole 4a of the mover 4. The mover 4 is rotated by the circular motion of the driver 3, and the mover 4 is moved in a shaft direction in response to the locus of the screw. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is a vibration type in which a driving body is vibrated by a driving element such as a piezoelectric element, and a moving body fitted to a vibrating driving body via a screw portion is moved in an axial direction. It relates to an actuator.

  The following Patent Document 1 and Patent Document 2 disclose a vibration type actuator having a driving body and a moving body that are fitted to each other via a screw portion, and a piezoelectric element that vibrates the driving body.

  When the driving body is vibrated by the piezoelectric element, the vibration of the driving body is transmitted to the moving body and the moving body is rotated. Since the moving body is fitted to the driving body via the screw portion, the rotating moving body is moved along the screw portion in the axial direction. This type of vibration type actuator has an advantage that a moving body can move forward and backward in the axial direction while rotating at a relatively low speed, and a large driving torque can be obtained.

  The vibration-type actuator described in Patent Document 1 is a shaft body having a male body in which a driving body is a cylindrical body having a female thread portion and a moving body is screwed into the female thread portion of the cylindrical body. A piezoelectric element is attached to the end face of the cylindrical driving body. With this piezoelectric element, a traveling wave is generated in the cylindrical driving body to apply a rotational force to the moving body. It is moved in the direction along the central axis of.

The vibration type actuator described in Patent Document 2 is provided with female screw members at both ends of a shaft hole of a cylindrical drive body, and male screws fitted into the respective female screw members inside the cylindrical drive body. A shaft-like moving body having a portion is provided. A piezoelectric element is provided on the outer surface of the cylindrical driving body, and the cylindrical driving body is deformed by the piezoelectric element so as to bend, and a circular motion is given to the female screw member. Thereby, the movable body on the shaft fitted to the female screw member is rotated, and the movable body advances in the axial direction.
Japanese Patent Publication No. 7-40791 US Patent Specification No. 6,940,209

  In the vibration type actuator described in Patent Document 1, a piezoelectric element is attached to an end face of a cylindrical drive body, and a traveling wave is transmitted to the drive body by distortion applied from the piezoelectric element to the end face. However, in order to generate a traveling wave on the inner peripheral surface of the cylindrical driving body, it is necessary to give a large strain to the end face from the piezoelectric element, and the energy utilization efficiency is extremely poor. In addition, if the piezoelectric element cannot be attached to the end face of the drive body with high accuracy, the efficiency of generating a traveling wave in the drive body is deteriorated. Furthermore, since the variation in the thickness of the adhesive for attaching the piezoelectric element to the end face affects the vibration characteristics of the driving body, the attaching operation using the adhesive is very difficult.

  Next, in the vibration type actuator described in Patent Document 2, a plurality of piezoelectric elements are attached to the outer surface of the cylindrical driving body in order to bend and deform the cylindrical driving body provided with a screw member inside. Yes. Since it is necessary to attach the plurality of piezoelectric elements so as not to incline linearly in the axial direction on the outer surface of the driving body, the attaching operation is extremely difficult. Further, it is necessary to apply an adhesive for adhering the piezoelectric element to the driving body with a uniform thickness in the axial direction, and the attaching operation is complicated.

  Moreover, since the attachment plane for sticking a piezoelectric element is formed in an axial direction on the outer surface of a cylindrical drive body, the cross-sectional shape of a drive body becomes a polygon. Therefore, when the bending direction of the driving body changes, the section modulus differs, and it is difficult to smoothly circularly move the female screw portion due to the bending deformation of the driving body.

  The present invention solves the above-described conventional problems, has high energy use efficiency when the driving body is vibrated by the driving force of the driving element, can simplify the shape of the driving body, and is easy to manufacture. An object of the present invention is to provide a vibration type actuator capable of realizing a highly accurate operation.

The vibration type actuator of the present invention includes a moving body in which a thread portion is continuously formed in the axial direction, and a driving fitting that is elastically deformable and that fits the thread portion of the moving body in a part of the axial direction. A drive body having a portion, a support body for supporting the drive body,
A driving element that applies vibration to the support and transmits vibration from the support to the driving body to bend and deform the driving body;
The drive fitting portion is caused to perform a circular motion due to the bending deformation of the drive body, the movable body is rotated by the circular motion, and the movable body is moved in the axial direction by the screw portion. It is.

  In the present invention, the driving body is caused to resonate by vibration applied from the driving element to the support body.

  Further, the driving fitting portion is provided between the nodes of the flexural vibration of the driving body.

  In the vibration type actuator of the present invention, the drive element is not directly attached to the drive body, but vibration is applied from the drive element to the support body, and this vibration is transmitted to the drive body, so that the drive body is It can be vibrated at the frequency. Therefore, the work of attaching the piezoelectric element or the like with high accuracy without inclining along the axial direction of the driving body becomes unnecessary, and the manufacturing can be facilitated. In addition, when a piezoelectric element is attached to the drive body, there is no problem of deviation of the mass distribution due to variations in the thickness of the adhesive, and the occurrence of variation in the mass of the drive body can be suppressed, and the drive body is always highly accurate. Can be driven in various vibration modes.

  In the present invention, the support is provided with a plane orthogonal to the axis of the drive body, the drive element is attached to the plane, and the drive element is mutually attached to the axis center of the drive body. Exciting forces that are orthogonal and have different phases are applied.

  In the present invention, it is preferable that a hole is opened in the support body on an extension of an axial center of the driving body.

  If a hole located on the support is located on the extension of the axis of the drive body, a circular motion is generated at the connecting part between the drive body and the support body due to the vibration applied to the support body from each drive element. This makes it easier to vibrate the driving body in the resonance mode.

  Furthermore, in the present invention, it is preferable that a hole positioned between adjacent drive elements is formed in the support.

  Drive elements arranged at adjacent positions orthogonal to each other on the plane of the support generate vibrations having different phases from each other, but differ if holes are formed in the support between adjacent drive elements. Due to the vibration of the phase, unnecessary wavy vibration is hardly generated on the plane of the support.

  In the present invention, for example, the driving body is an elastically deformable vibration shaft, the moving body is a cylindrical body having an internal thread formed on an inner peripheral surface, and the driving fitting portion is the vibration shaft. It is the external thread part provided in.

  In this case, since it is not necessary to attach a driving element such as a piezoelectric element to the outer peripheral surface of the vibration shaft, the outer peripheral surface of the vibration shaft can be a cylindrical surface. Therefore, it is easy to manufacture the vibration shaft. Furthermore, when the outer peripheral surface is a cylindrical surface, the vibration axis can have substantially the same section modulus regardless of the direction of bending. Therefore, it is easy to generate the flexural vibration in which the driving fitting portion moves circularly.

  Alternatively, in the present invention, the driving body is an elastically deformable vibration cylinder, the moving body is a shaft body having a male screw portion formed on an outer peripheral surface, and the driving fitting portion is the vibration cylinder. It is the internal thread part provided in the internal peripheral surface of the body.

  Also in this case, the outer peripheral surface of the vibrating cylinder can be a cylindrical surface, and the section modulus can be made almost equal regardless of the direction of bending of the vibrating cylinder.

  In the present invention, the support body is vibrated by the drive element, and the vibration of the support body is transmitted to the drive body to vibrate the drive body. Therefore, there is no need to attach a driving element such as a piezoelectric element to the driving body, the shape of the driving body can be simplified, and manufacturing is easy. In addition, the driving body can be formed in a circular shape, and the section modulus in each bending direction can be made substantially uniform, and it is easy to generate a highly accurate circular motion in the driving screw portion.

  FIG. 1 is a perspective view showing a vibration type actuator according to a first embodiment of the present invention with a moving body removed, and FIG. 2 is a plane perpendicular to the axis center of the vibration type actuator according to the first embodiment. FIG. 3 is a longitudinal sectional view of the vibration type actuator cut along a plane including the axial center. 4 and 5 are explanatory diagrams showing the connection structure between the piezoelectric element and the drive circuit, and FIG. 6 is a waveform diagram showing the phase of the drive signal applied to the piezoelectric element. FIGS. 7A and 7B are explanatory diagrams showing resonance modes of the vibration type actuator according to the first embodiment for each model. FIG. 8 is an explanatory diagram of a vibration mode model of the vibration type actuator according to the modification of the first embodiment.

  The vibration type actuator 1 shown in FIG. 1 is a cylindrical body having a center hole 4a through which the driving body is the vibration shaft 2 and the moving body 4 penetrates in the vertical direction (Z-axis direction). An internal thread portion 14 that is continuous in the axial direction is formed on the inner peripheral surface of the center hole 4 a of the moving body 4. A drive element 3 is fixed at the axial center of the vibration shaft 2, and a male screw part 13 that functions as a drive fitting part is formed on the outer peripheral surface of the drive element 3.

  The vibration shaft 2 is formed of an elastic material such as a metal or a synthetic resin material, and is a solid shaft or a hollow shaft whose axial center O1 is a straight line when no external force is applied. The vibration shaft 2 can be bent so that the shaft center O1 is curved. As a result, the driver 3 fixed to the vibration shaft 2 performs a circular motion. Therefore, it is preferable that the bending rigidity is almost equal in any direction in the XY coordinate plane orthogonal to the axis center O1, and for that purpose, the section modulus of the vibration shaft 2 is uniform in any direction. It is preferable. Since the vibration type actuator 1 does not require a piezoelectric element to be attached to the outer peripheral surface of the vibration shaft 2, the outer peripheral surface of the vibration shaft 2 can be a cylindrical surface, and the cross-sectional shape of the vibration shaft 2 cut along the XY plane can be obtained. It can be a solid circle or a hollow circle (cylindrical shape). Therefore, the vibration axis 2 has a uniform section modulus with respect to any direction on the XY plane.

  When the outer peripheral surface of the vibration shaft 2 is a cylindrical surface, the vibration shaft can be manufactured with a round bar-shaped shaft or a cylindrical body, and the manufacturing cost can be reduced. In addition, the mass distribution in the axial direction of the vibration shaft 2 can be made uniform.

  As shown in FIG. 1, the vibration shaft 2 is fixed with a lower end portion of the vibration shaft 2 held by a support 5, and the upper end portion of the vibration shaft 2 is a free end. As shown in FIG. 1, the support 5 is a plate material that exhibits a certain thickness of elastic force, and is a metal plate, a synthetic resin plate, or a ceramic plate. A center hole 5a is formed through the support 5 and the lower end portion of the vibration shaft 2 is inserted into the center hole 5a and fixed to the support 5 by means such as welding. Alternatively, the lower end portion of the vibration shaft 2 is press-fitted into the center hole 5a and fixed. In a state where no driving force is applied to the vibration shaft 2, the axis center O <b> 1 of the vibration shaft 2 is perpendicular to the surface 5 b of the support 5.

  Four piezoelectric elements 6, 7, 8, and 9 are attached to the surface 5 b of the support 5 as drive elements. The piezoelectric elements 6, 7, 8, 9 are made of a piezoelectric ceramic that exhibits an electrostrictive effect, and the direction of dielectric polarization of each of the piezoelectric elements 6, 7, 8, 9 is the thickness direction (Z direction).

  The piezoelectric element 6 and the piezoelectric element 7 are located on a line extending in the X direction through the center O2 of the lower end portion of the vibration shaft 2. The piezoelectric element 6 is located on the + X side with respect to the center O2, and the piezoelectric element 7 is located on the −X side with respect to the center O2. In the piezoelectric element 6, an electrode 6 b is provided on a surface of the upper surface (+ Z side) where the electrode 6 a faces the surface 5 b of the support 5. In the piezoelectric element 7, an electrode 7 b is provided on the upper surface (+ Z side) of the electrode 7 a on the surface facing the front surface 5 b of the support 5.

  When the support 5 is made of metal and the support 5 is set to the ground potential, the electrodes 6b and 7b are electrically connected to the support 5 as shown in FIGS. Thus, the electrodes 6b and 7b are set to the ground potential. When the support 5 is made of metal and a drive voltage other than the ground potential is applied to the electrodes 6b and 7b, an insulating layer is provided between the electrodes 6b and 7b and the surface 5b of the support 5.

  The piezoelectric element 8 and the piezoelectric element 9 are located on a line extending in the Y direction through the center O2 of the lower end portion of the vibration shaft 2. The piezoelectric element 8 is located on the + Y side with respect to the center O2, and the piezoelectric element 9 is located on the −Y side with respect to the center O2. In the piezoelectric element 8, an electrode 8 b is provided on a surface of the upper surface (+ Z side) where the electrode 8 a faces the surface 5 b of the support 5. In the piezoelectric element 9, an electrode 9 a is provided on the upper (+ Z side) surface, and an electrode 9 b is provided on the surface of the support 5 that faces the front surface 5 b.

  When the support 5 is made of metal and the support 5 is set to the ground potential, the electrodes 8b and 9b are electrically connected to the support 5 as shown in FIGS. Thus, the electrodes 8b and 9b are set to the ground potential. When the support 5 is made of metal and a drive voltage other than the ground potential is applied to the electrodes 8b and 9b, an insulating layer is provided between the electrodes 8b and 9b and the surface 5b of the support 5.

  The piezoelectric element 6 and the piezoelectric element 7 have the longitudinal direction oriented in the X direction, and the width dimension in the Y direction is sufficiently shorter than the dimension in the longitudinal direction. Therefore, when a drive signal (drive voltage) is applied between the electrodes 6a and 6b and a volume change occurs in the piezoelectric element 6, an elongation stress or a contraction stress mainly in the X direction from the piezoelectric element 6 to the support 5 is obtained. Is given. Similarly, an elongation stress or a contraction stress in the X direction is applied from the piezoelectric element 7 to the support 5. The piezoelectric element 6 and the piezoelectric element 7 operate so that when one extends in the X direction, the other contracts in the X direction.

  The piezoelectric element 8 and the piezoelectric element 9 have a long shape in which the longitudinal direction is directed in the Y direction and the width dimension in the X direction is sufficiently shorter than the dimension in the longitudinal direction. Therefore, when a drive signal (drive voltage) is applied between the electrodes 8a and 8b and a drive signal (drive voltage) is applied between the electrodes 9a and 9b, the piezoelectric element 8 and the piezoelectric element 9 are applied to the support 5 with respect to the support body 5. Elongation stress and shrinkage stress in the Y direction are mainly given. The piezoelectric element 8 and the piezoelectric element 9 operate so that when one extends in the Y direction, the other contracts in the Y direction.

  As shown in FIG. 1, a fan-shaped through hole 5d is provided between adjacent piezoelectric elements. The distortion applied to the support 5 from each of the piezoelectric elements 6, 7, 8, 9 is blocked by the through-hole 5 d, and unnecessary wave-like distortion from the piezoelectric elements 6, 7, 8, 9 to the support 5. Can be prevented from being given. Therefore, the elongation stress and the contraction stress applied from the piezoelectric elements 6, 7, 8, 9 to the support body 5 easily act in the X direction and the Y direction with respect to the center O 2 of the lower end portion of the vibration shaft 2. Further, since the support 5 has a central hole 5a located coaxially with the vibration axis 2, the vibration axis 2 is caused by stress applied to the support 5 from the piezoelectric elements 6, 7, 8, and 9. It becomes easy to give a vibration to the center O2 of the lower end part of. That is, the stress in the X direction applied from the piezoelectric elements 6 and 7 to the support body 5 and the stress in the Y direction applied from the piezoelectric elements 8 and 9 to the support body 5 are transmitted through the center hole 5a. It becomes easy to act on the center O2 of the lower end part.

  As a result, by giving drive signals having a phase difference of 90 degrees to the piezoelectric elements 6 and 7 and the piezoelectric elements 8 and 9, the center O2 of the lower end portion of the vibration shaft 2 is likely to cause a circular motion.

  As shown in FIGS. 2 and 3, the driver 3 is made of metal or synthetic resin, and an inner peripheral surface thereof is inserted and fixed to the outside of the vibration shaft 2. The driver 3 and the vibration shaft 2 may be integrally formed of a metal material or the like. A male screw portion 13 that functions as a driving fitting portion is formed on the outer peripheral surface of the driver element 3.

  In the example of FIG. 1, the driver element 3 is arranged at the midpoint of the length of the vibration shaft 2, but the optimum position of the driver element 3 is determined according to the mode of flexural resonance of the moving shaft 2. For this reason, it may be optimal to provide the drive element 3 at the free end of the vibration shaft 2, and it may be optimal to provide the drive element 3 at a position other than the midpoint of the vibration shaft 2. In any case, the vibrator 3 is preferably provided at a midpoint between vibration nodes in the resonance mode of the vibration shaft 2.

  The cylindrical moving body 4 is made of metal, and an internal thread portion 14 is formed over the entire length in the axial direction on the inner peripheral surface of the center hole 4a. The moving body 4 preferably has a large inertial force, and for that purpose, the mass is preferably large. It is preferable that the mass of the movable body 4 is larger than the sum of the mass of the vibration shaft 2 and the mass of the driver 3, that is, the sum of the masses of the vibrating portions.

  The internal thread portion 14 formed on the inner peripheral surface of the center hole 4 a of the moving body 4 has the same pitch as the external thread portion 13 formed on the outer peripheral surface of the driver 3, but the effective diameter of the internal thread portion 14. Is slightly larger than the effective diameter of the male screw portion 13. Therefore, as schematically shown in FIGS. 2 and 3, when the female screw portion 14 of the moving body 4 is fitted to the male screw portion 13 of the driver 3, the moving body 4 moves in a direction orthogonal to the axial center O <b> 1. Although it has some shakiness, even if the moving body 4 is moved in the direction along the axial center O1, the thread of the female screw portion 14 does not exceed the screw thread of the male screw portion 13. That is, the moving body 4 is fitted to the driver element 3 so as to rattle in the axial direction, but the moving body 4 is not pulled out of the driver element 3 in the axial direction.

  FIG. 4 shows an A-phase drive signal generator (AC voltage generator) 21 and a B-phase drive signal generator (AC voltage generator) 22 as the drive circuit 20. In the vibration type actuator 1 according to this embodiment, the piezoelectric elements 6, 7, 8, 9 and the drive circuit 20 constitute vibration means. As shown in the waveform diagram of FIG. 6, the A + phase drive signal (voltage) generated by the A phase drive signal generator 21 and the B + phase drive signal (voltage) generated by the B phase drive signal generator 21 (see FIG. 6). (Voltage) are 90 degrees out of phase with each other, one of which is approximately a sine wave and the other is approximately a cosine wave. The B + phase is 90 degrees ahead of the A + phase. The A-phase drive signal and the B-phase drive signal may be rectangular waves having different phases. Even when a rectangular wave is applied to the piezoelectric elements 6, 7, 8, 9, a sine wave and cosine are applied to the piezoelectric elements 6, 7, 8, 9 due to a delay in electrical signal transmission and a delay in mechanical electrostriction effect. It can be driven in the same way as a wave is applied.

  In the connection structure shown in FIG. 4, the dielectric polarization direction of the piezoelectric elements 6 and 9 is the −Z direction, and the dielectric polarization direction of the piezoelectric elements 7 and 8 is the + Z direction. The electrodes 6b, 7b, 8b, 9b of the piezoelectric elements 6, 7, 8, 9 are fixed in contact with the metal support 5, and the electrodes 6b, 7b, 8b, 9b are set to the ground potential. ing.

  The A + phase drive signal from the A phase drive signal generator 21 is applied to the front electrode 6 a of the piezoelectric element 6 and the front electrode 7 a of the piezoelectric element 7. Also, the B + phase drive signal from the B phase drive signal generation unit is applied to the front electrode 8 a of the piezoelectric element 8 and the front electrode 9 a of the piezoelectric element 9. The A-side of the drive signal generation unit 21 and the B-side of the drive signal generation unit 22 are set to the ground potential.

  In the connection structure shown in FIG. 4, substantially sine waves and substantially cosine waves obtained by the oscillation circuits in the respective drive signal generation units 21 and 22 are converted to the electrodes 6 a and 7 a on the front side of the piezoelectric elements 6, 7, 8 and 9. , 8a, 9a, the circuit configuration can be simplified.

Next, the operation of the vibration type actuator 1 will be described.
In the connection structure shown in FIG. 4, the dielectric polarization directions of the piezoelectric element 6 and the piezoelectric element 7 are opposite to each other, and the same A + phase drive signal is applied to the electrodes 6a and 7a. Therefore, when one of the piezoelectric element 6 and the piezoelectric element 7 applies an elongation stress in the X direction to the support 5, the other simultaneously applies a contraction stress in the X direction to the support 5. Therefore, the center O2 of the lower end portion of the vibration shaft 2 located between the piezoelectric element 6 and the piezoelectric element 7 reciprocates in the + X direction and the −X direction at the same frequency as the frequency of the A + phase, and the center at this time The change in position with respect to time of O2 almost corresponds to a sine function.

  In addition, since the dielectric polarization directions of the piezoelectric element 8 and the piezoelectric element 9 are opposite to each other, when a B + phase drive signal is simultaneously applied to the electrode 8a and the electrode 9a, one of the piezoelectric element 8 and the piezoelectric element 9 becomes the support 5. Is given an elongation stress in the Y direction, while the other gives a shrinkage stress in the Y direction to the support 5. The center O2 of the lower end portion of the vibration shaft 2 between the piezoelectric element 8 and the piezoelectric element 9 reciprocates in the + Y direction and the −Y direction at the same frequency as the frequency of the B + phase, and the position of the center O2 with respect to time at this time The change of is almost coincident with the cosine function.

  That is, the A + phase and the B + phase are different by 90 degrees, and the A + phase and the B + phase have the same frequency. Therefore, as described above, the A + phase and the B + phase have a sine function and a cosine function. The center O2 is a combined motion of a sine function and a cosine function, and thus the center O2 performs a circular motion.

  In the connection structure shown in FIG. 4, for example, the piezoelectric element 7 contracts and the piezoelectric element 6 extends at time (a) shown in FIG. 6, and the piezoelectric element 8 contracts and piezoelectric element at a subsequent time (b). Since 9 extends, the center O2 of the lower end portion of the vibration shaft 2 moves in a clockwise direction as viewed from above.

  In FIG. 4, when the circuit is switched such that an A + phase drive signal is applied to the electrodes 8a and 9a of the piezoelectric elements 8 and 9 and a B + phase drive signal is applied to the electrodes 6a and 7a of the piezoelectric elements 6 and 7, The rotation direction of O2 is counterclockwise.

FIG. 5 shows another connection structure between the piezoelectric elements 6, 7, 8 and 9 and the drive circuit 20.
In the connection structure shown in FIG. 5, the dielectric polarization directions of all the piezoelectric elements 6, 7, 8, 9 are directed to the same −Z direction. Further, the electrodes 6b, 7b, 8b, 9b provided on the −Z side surface of all the piezoelectric elements 6, 7, 8, 9 are connected and fixed to the front surface 5b of the metal support 5. In addition to the support 5, the electrodes 6b, 7b, 8b, 9b are set to the ground potential.

  The A + phase drive signal generated by the A phase drive signal generation unit 21 is applied to the front electrode 6a of the piezoelectric element 6, and the phase of the A + phase drive signal is inverted by 180 degrees by the phase inverter 23. And applied to the front electrode 7 a of the piezoelectric element 7. The B + phase drive signal generated by the B phase drive signal generation unit 22 is applied to the front electrode 9a of the piezoelectric element 9, and the B + phase drive signal is inverted in phase by the phase inversion circuit 24. 8 is applied to the front electrode 8a.

  In the connection structure shown in FIG. 5, the dielectric polarization direction of the piezoelectric elements 7 and 8 is the −Z direction, which is opposite to the + Z direction dielectric polarization direction in the connection structure shown in FIG. 4. However, in FIG. 5, the A + phase drive signal is inverted and applied to the electrode 7 a of the piezoelectric element 7, and the B + phase drive signal is inverted and applied to the electrode 8 a of the piezoelectric element 8.

  Therefore, in the connection structure shown in FIG. 5, the center O2 of the lower end portion of the vibration shaft 2 circularly moves clockwise as viewed from above, similarly to the connection structure shown in FIG. In the connection structure of FIG. 5, when the A + phase drive signal and the B + phase drive signal are switched so as to be switched, the direction of the circular motion of the center O2 is switched counterclockwise.

  In the connection structure shown in FIG. 5, all the piezoelectric elements 6, 7, 8, 9 have the same dielectric polarization direction.

  The frequency of the A + phase drive signal given to the piezoelectric elements 6 and 7 from the drive signal generation unit 21 and the frequency of the B + phase drive signal given to the piezoelectric elements 8 and 9 from the drive signal generation unit 22 are the vibration axis 2. Is set to a value that can bend and vibrate at the natural frequency. That is, the vibration shaft 2 is bent in the resonance mode shown in FIG. 7 and FIG. 8 by the A + phase drive signal and the B + phase drive signal, and the center O2 of the lower end is circularly moved. The part also moves circularly in a deformed state corresponding to the resonance mode.

  The natural frequency of the bending of the vibration shaft 2 is determined by the mass of the vibration shaft 2 and the mass of the driver 3, the length of the vibration shaft 2, and the elastic coefficient of the bending deformation of the vibration shaft 2. Note that the mass of the driver element 3 is not so large as compared with the entire mass of the vibration shaft 2, and therefore the masses of the vibration shaft 2 and the driver element 3 are substantially uniform in the axial direction of the vibration shaft 2. It is equal to being distributed. Therefore, the natural frequency of the vibration shaft 2 is approximately equivalent to the natural frequency of a cantilever beam whose mass is evenly distributed in the axial direction. However, in actuality, the moving body 4 and the moving body 4 vibrate together, so the mass and length of the moving body are one of the factors that determine the natural frequency of the vibrating shaft 2.

  7A and 7B show the two resonance modes of the vibration axis 2 for each model. The resonance mode in FIG. 7A is a resonance in which the entire length of the vibration axis 2 corresponds to approximately one wavelength. The driver 3 is located at the midpoint between the vibration nodes, and the amplitude of the circular motion is maximized at the portion of the driver 3. In the energized state shown in FIGS. 4 and 5, the driver element 3 moves in a clockwise direction when viewed from above. In the resonance mode shown in FIG. 7B, one wavelength is almost four times the entire length of the vibration axis 2. The vibration shaft 2 has the maximum circular motion amplitude at the center O2 at the lower end thereof, and the driver 3 is positioned at the midpoint between the maximum amplitude portion and the vibration node, and moves in a clockwise direction. To do. It is also possible to resonate the vibration shaft 2 at a higher natural frequency than in FIGS. 7 (A) and 7 (B).

  When the vibration shaft 2 bends, deforms and vibrates in the resonance mode shown in FIGS. 7A and 7B and the driver element 3 moves in a clockwise direction, the male screw portion 13 of the driver element 3 causes the cylindrical moving body 4 to move. A clockwise rotational force is applied to the female screw portion 14. Therefore, the moving body 4 advances downward in the figure (−Z direction) according to the spiral locus of the female screw portion 14 while being rotated clockwise.

  In addition, the energization states of the A + phase drive signal and the B + phase drive signal to the electrodes of the piezoelectric elements 6, 7, 8, and 9 are switched so as to be opposite to those in FIGS. 4 and 5. When the center O2 of the lower end portion moves in a counterclockwise direction, the resonant driving element 3 also moves in a counterclockwise direction as viewed from above.

  At this time, a counterclockwise rotational force is applied from the male screw portion 13 of the driver 3 to the female screw portion 14 of the moving body 4. Therefore, the moving body 4 proceeds in the upward direction (+ Z direction) according to the spiral locus of the female screw portion 14 while being rotated counterclockwise.

  FIG. 8 shows a resonance mode of the vibration type actuator 1A which is a modification of the first embodiment.

  In the vibration type actuator 1A, a driver element 3 having a male screw portion 13 is fixed to the upper end of the vibration shaft 2. The vibration means for resonating the vibration shaft 2 is the same as that of the first embodiment shown in FIGS. A force that causes circular motion in the XY plane is applied to the center O2 of the lower end portion of the vibration shaft 2 by the vibration means. In this case, one wavelength of the resonance mode is twice the total length of the vibration axis 2 in the axial direction.

  In the vibration type actuator 1A shown in FIG. 8, the driving element 3 provided at the upper end of the vibration shaft 2 performs a circular motion in a resonance state, so that a rotational force is applied to the moving body 4 by the driving element 3, and the female screw portion 14 The moving body 4 is moved in the + Z direction or the −Z direction by the locus.

  FIG. 9 is a longitudinal sectional view showing the vibration type actuator 101 according to the second embodiment of the present invention.

  In the vibration type actuator 101 shown in FIG. 9, the driving body is a vibration cylinder 104, and the lower end portion of the vibration cylinder 104 is inserted into a center hole 5 a formed in the support body 5 and fixed. A driver element 103a is fixed to the upper end portion of the center hole 104a of the vibrating cylinder 104, and a driver element 103b is fixed to the lower end portion of the center hole 104a. Each of the driver elements 103 a and 103 b has a ring shape, and the outer peripheral surface thereof is fixed to the inner peripheral surface of the center hole 104 a of the vibrating cylinder 104. A female screw portion 14a and a female screw portion 14b functioning as a driving fitting portion are formed on the inner peripheral surfaces of the driver elements 103a and 103b.

  As shown in FIG. 1, piezoelectric elements 6, 7, 8, and 9 are fixed to the front surface 5 b of the support 5, and through holes 5 d are formed between adjacent piezoelectric elements.

  The moving body 102 is a shaft body, and the center of the axis is linear. A male screw portion 13 that is continuous in the axial direction is formed on the outer peripheral surface of the moving body 102. The dimensional relationship and fitting state between the effective diameters of the female screw portions 14a and 14b and the male screw portion 13 are the same as those of the male screw portion 13 and the female screw portion 14 in the first embodiment shown in FIGS. Same as mating. A male screw portion that fits with the upper female screw portion 14a is formed in the upper portion of the moving body 102 that is a shaft body, and a male screw portion that fits with the lower female screw portion 14b is formed in the lower portion of the moving body 102. The outer peripheral surface of the shaft body which is formed and between which the male screw part is not engraved may appear between the male screw part of the upper part and the male screw part of the lower part.

  In this vibration type actuator 101, as in the first embodiment, elongation stress and contraction stress are applied to the support body 5 from the piezoelectric elements 6, 7, 8, 9 serving as vibration means, and the vibration cylinder 104 The center of the lower end of the circle moves circularly. By matching the frequency of this circular motion with the natural frequency of the vibrating cylinder 104, the vibrating cylinder 104 resonates so as to cause a circular movement without being deformed.

  10A and 10B show examples of resonance modes at this time. The resonance frequency is determined by the mass of the vibrating cylinder 104 and the masses of the driver elements 103a and 103b, the length of the vibrating cylinder 104, and the elastic coefficient of the deflection deformation of the vibrating cylinder 104. However, since the moving body 102, which is a shaft body, also operates together, the mass and length of the moving body 102 also determine the resonance frequency.

  In the resonance mode shown in FIG. 10A, one wavelength is approximately twice the length of the vibrating cylinder 104. In the resonance mode shown in FIG. 10B, the length of the vibrating cylinder 104 is substantially equivalent to one wavelength.

  In any of the resonance modes, when the driver element 103a and the driver element 103b provided on the vibrating cylinder 104 perform a circular motion in the clockwise direction when viewed from above, the female screw portions 14a and 14b formed on the driver elements 103a and 103b The moving body 102 is rotated clockwise. Therefore, the moving body 102 advances in the −Z direction according to the spiral trajectory of the male screw portion 13. When the drive elements 103a and 103b resonate so as to make a circular motion counterclockwise when viewed from above, the moving body 102 is rotated counterclockwise by the female screw portions 14a and 14b and proceeds in the + Z direction.

  FIGS. 11A and 11B show vibration type actuators 101A and 101B which are modifications of the second embodiment.

  A vibration type actuator 101A shown in FIG. 11A includes a vibration cylinder 104 as a driving body and a moving body 102 as a shaft. In the center hole 104a of the vibration cylinder 104, one driver element 103 is fixed at a position that is half the axial length, and an internal thread portion 14 that functions as a drive fitting portion is formed on the inner surface of the driver element 103. Is formed. In the resonance mode of the vibrating cylinder 104 shown in FIG. 11A, the entire length of the vibrating cylinder 104 is substantially equivalent to one wavelength.

  In the vibration type actuator 101 </ b> B shown in FIG. 11B, the driver element 103 is provided at the lower end of the vibration cylinder 104, that is, the part supported by the support body 5, and the female screw part 14 is formed in the driver element 103. ing. In this example, the vibrating cylinder 104 is driven in a resonance mode whose full length corresponds to a quarter wavelength.

  In the vibration type actuators 101, 101A, 101B shown in FIGS. 9 to 11, the vibration cylinder 104, which is a drive body, bends and vibrates at a resonance frequency, and the drive elements 103, 103a, 103b have vibration nodes and nodes. It is fixed between and moves circularly. Therefore, the vibrating cylinder 104 can be effectively resonated by the piezoelectric elements 6, 7, 8, and 9, and the moving body 102 can be reliably advanced and retracted.

FIG. 12 shows a vibration type actuator 201 according to the third embodiment of the present invention.
In the vibration type actuator 201, the midpoint of the axial length of the vibration cylinder 204 as a driving body is inserted into the center hole 5 a of the support 5 and fixed. As shown in FIG. 1, piezoelectric elements 6, 7, 8, and 9 that constitute vibration means are fixed to the support 5. A drive element 203 is fixed to an intermediate point of the axial length of the vibration cylinder 204, that is, an inner peripheral surface of a portion held by the support body 5, and a driving fitting is fitted to the inner peripheral surface of the drive element 203. A female screw portion 14 that functions as a portion is formed. The moving body 202 is a shaft body, and an external thread portion 13 that is continuous in the axial direction is formed on the outer peripheral surface. The female screw portion 14 and the male screw portion 13 of the driver 203 are fitted.

  The piezoelectric element 6, 7, 8, 9 gives an extension strain and a contraction strain to the support 5, and the vibration cylinder 204 is driven in the resonance mode shown in FIG. 13A or the resonance mode shown in FIG. The The driver 203 is fixed to a portion having the largest amplitude between the vibration nodes and performs a circular motion.

  As shown in FIG. 4 or 5, when the piezoelectric elements 6, 7, 8, and 9 are energized, the driver 203 moves circularly, and the moving body 202, which is a shaft body, is rotated by the female screw portion 14. Direction or -Z direction.

  When driving in the resonance mode shown in FIG. 13B, the driver 203 is not provided at the same position as the support 5, but the driver 203 is provided at each of the upper end and the lower end of the vibrating cylinder 204. It may be fixed.

  In each of the above embodiments, the piezoelectric elements 6, 7, 8, and 9 are used as drive elements that apply stress for vibration to the support 5. However, as drive elements that cause vibration to act on the support 5. Electromagnetic actuators other than piezoelectric elements, electrostatic actuators, thermal stress generating elements, or the like may be used.

The perspective view which shows the vibration type actuator of the 1st Embodiment of this invention in the state which removed the moving body, A cross-sectional view of the vibration type actuator of the first embodiment, A longitudinal sectional view of the vibration type actuator of the first embodiment, Explanatory drawing which shows the connection structure of a piezoelectric element and a drive circuit, Explanatory drawing which shows the other example of the connection structure of a piezoelectric element and a drive circuit, Waveform diagram of A phase drive signal and B phase drive signal, (A) (B) is a model explanatory view of a resonance mode of the vibration type actuator of the first embodiment, FIG. 5 is a model explanatory diagram of a resonance mode of a vibration type actuator according to a modification of the first embodiment; The longitudinal cross-sectional view of the vibration type actuator of the 2nd Embodiment of this invention, (A) (B) is a model explanatory view of a resonance mode of the vibration type actuator of the second embodiment, (A) (B) is a model explanatory view of a resonance mode of a vibration type actuator of a modification of the second embodiment, The longitudinal cross-sectional view of the vibration type actuator of the 3rd Embodiment of this invention, (A) (B) is a model explanatory view of a resonance mode of the vibration type actuator of the third embodiment,

Explanation of symbols

1 Vibrating actuator 2 Vibrating shaft (Driver)
3 driver 4 moving body 4a center hole 5 support body 5a center hole 5b surface plane 5d through hole 6, 7, 8, 9 piezoelectric element 6a, 6b, 7a, 7b, 8a, 8b, 9a, 9b electrode 13 male screw part 14 Female screw portion 20 Drive circuit 101 Vibrating actuator 102 Moving body 103, 103a, 103b Driving element 104 Vibrating cylinder 201 Vibrating actuator 202 Moving body 203 Driving element 204 Vibrating cylinder

Claims (10)

A moving body in which a threaded portion is formed continuously in the axial direction, a driving body that is elastically deformable and has a driving fitting portion that fits the threaded portion of the moving body in a part of the axial direction; A support for supporting the drive body;
A driving element that applies vibration to the support and transmits vibration from the support to the driving body to bend and deform the driving body;
The drive fitting portion circularly moves due to bending deformation of the drive body, the movable body is rotated by the circular motion, and the movable body is moved in the axial direction by the screw portion. Type actuator.   The vibration type actuator according to claim 1, wherein the drive body is resonated by vibration applied to the support body from the drive element.   The vibration actuator according to claim 1, wherein the driving fitting portion is provided between nodes of flexural vibration of the driving body.   The support is provided with a plane orthogonal to the axis of the drive body, the drive element is attached to the plane, and the drive element is oriented perpendicular to the axis center of the drive body. 4. The vibration type actuator according to claim 1, wherein excitation forces having different phases are applied.   The vibration type actuator according to claim 4, wherein a hole is opened in the support body on an extension of an axial center of the driving body.   6. The vibration type actuator according to claim 4, wherein the support is formed with a hole positioned between adjacent drive elements.   The drive body is an elastically deformable vibration shaft, the moving body is a cylindrical body having an internal thread portion formed on an inner peripheral surface, and the drive fitting portion is an external thread portion provided on the vibration shaft. The vibration type actuator according to any one of claims 1 to 6.   The vibration type actuator according to claim 7, wherein an outer peripheral surface of the vibration shaft is a cylindrical surface.   The drive body is an elastically deformable vibration cylinder, the moving body is a shaft body having an external thread formed on an outer peripheral surface, and the drive fitting portion is formed on an inner peripheral surface of the vibration cylinder. The vibration type actuator according to claim 1, wherein the vibration type actuator is a female screw portion provided.   The vibration type actuator according to claim 9, wherein an outer peripheral surface of the vibration cylinder is a cylindrical surface.

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