JP2010142092A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor which can attains an improvement in efficiency of a motor by removing unnecessary bending vibration components other than torsional vibration thereby materializing appearance of stable elliptic vibration and achieving an improvement in sliding property, in simple structure. <P>SOLUTION: This ultrasonic motor is so structurized as to achieve matching between longitudinal vibration resonance frequency and torsional vibration resonance frequency by providing the flank of a bar-shaped elastic body 10 with a recess 9, corresponding to a stacked piezoelectric element 11, and reducing, with this recess 9, the displacement due to unnecessary bending vibration other than the torsional vibration by excitement of the torsional vibration of the bar-shaped elastic body 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrasonic motor used as an actuator such as a camera shake correction unit or an AF lens of a digital camera.

  In general, in this type of ultrasonic motor, a piezoelectric element, which is a vibrator, is applied with a voltage to excite longitudinal vibrations and torsional vibrations in a rod-like elastic body to generate elliptical vibrations. There is a configuration that rotationally drives a driven body that is a body.

  In such an ultrasonic motor, two stacked piezoelectric elements are arranged to be inclined with respect to the axial direction so as to face the side surface of the rod-shaped elastic body constituting the stator, and voltage is applied to the stacked piezoelectric element. By applying this, longitudinal vibration and torsional vibration are excited in the rod-shaped elastic body, and elliptical vibration is excited in the annular driver arranged on the end surface of the rod-shaped elastic body.

The rod-like elastic body is provided with a rotating shaft coaxially, and the driven body is rotatably mounted on the tip of the rotating shaft via a spring member. The driven body is supported by the spring member. The presser is disposed so as to be rotatable with respect to the driver. As a result, when elliptical vibration is excited in the driver, the driven body is rotated around the rotation axis using the elliptical vibration generated in the driver as a driving force (see, for example, Patent Document 1).
JP-A-8-317669

  The ultrasonic motor generates only longitudinal vibration when an alternating voltage having the same phase is applied to the left and right piezoelectric elements, and generates only torsional vibration when an alternating voltage having an opposite phase is applied. Therefore, an alternating voltage having a phase difference of 90 degrees is applied to generate longitudinal vibration and torsional vibration at the same time.

  However, in the structure in which the rod-shaped elastic body is sandwiched between the left and right laminated piezoelectric elements of the ultrasonic motor, the rod-shaped elastic body has a bending resonance vibration in a bending mode due to an expansion / contraction operation having a phase difference between the left and right laminated piezoelectric elements. Is likely to occur. Furthermore, depending on the structure of the rod-shaped elastic body, the natural resonance frequencies of the torsional resonance mode and the bending resonance mode may exist in the vicinity of the rod-shaped elastic body. In such a state, vibration is leaked between the laminated piezoelectric element and the rod-shaped elastic body, or vibration is transmitted, but a phase delay of the vibration is generated. If it is weak, the frequency component of the bending vibration is mixed in the resonance frequency band of the torsional vibration in accordance with the expansion / contraction operation of the multilayer piezoelectric element, and there is a disadvantage that uniform elliptical vibration does not occur in the driver. According to this, there is a problem that the motor sliding characteristic is lowered and the motor efficiency is lowered.

  The present invention has been made in view of the above circumstances, and with a simple configuration, unnecessary bending vibration components other than torsional vibrations are removed to realize stable elliptical vibration, thereby improving sliding characteristics. An object of the present invention is to provide an ultrasonic motor that can improve motor efficiency.

  Longitudinal and torsional vibrations are excited in the rod-like elastic body by stretching vibration of two stacked piezoelectric elements arranged opposite to the side surfaces of the rod-like elastic body according to the present invention, and provided on the end surface of the rod-like elastic body. The ultrasonic motor which excites elliptical vibration to the driven element and presses and arranges the driven body rotatably supported on the end surface of the rod-shaped elastic body with respect to the driver is friction-driven. A vibration buffer portion was provided on the side surface of the body corresponding to the laminated piezoelectric element.

  According to the above configuration, the vibration buffer transmits the torsional vibration of the rod-like elastic body, reduces displacement due to unnecessary bending vibration other than torsional vibration, and matches the longitudinal vibration resonance frequency and the torsional vibration resonance frequency. Thus, the elliptical vibration excited on the contact surface of the driver is stabilized. Thereby, highly efficient sliding characteristics can be obtained, and motor efficiency can be improved.

  As described above, according to the present invention, with a simple configuration, it is possible to remove unnecessary bending vibration components other than torsional vibrations and to generate stable elliptical vibrations, thereby improving sliding characteristics. An ultrasonic motor capable of improving motor efficiency can be provided.

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

  1 and 2 show an ultrasonic motor according to an embodiment of the present invention. FIG. 1 shows a state seen from the front side, and FIG. 2 shows the rod-like elastic body 10 seen from the side. Indicates the state.

  That is, the rod-like elastic body 10 is formed in a cylindrical shape with a metal material, for example, brass, and the first elastic portion 101 and the second elastic portion 102 are connected in a constricted shape with the groove portion 103 interposed therebetween. The full length of the rod-shaped elastic body 10 corresponds to, for example, the longitudinal vibration amplitude, and the length dimension of the first elastic portion 101 corresponds to the torsional vibration amplitude (see FIG. 3). Then, for example, two stacked piezoelectric elements 11 are provided on the side surface of the first elastic portion 101 so as to face each other with a predetermined inclination angle with respect to the axial direction.

  Further, the first elastic portion of the rod-shaped elastic body 10 includes a concave portion that constitutes a vibration buffering portion in the vicinity of the antinode of torsional vibration (near the position of the bending vibration) corresponding to the two laminated piezoelectric elements 11 on the side surface. 9 are respectively provided extending in a direction orthogonal to the longitudinal vibration direction of the columnar elastic body 10. The concave portion 9 includes at least a region in which the multilayer piezoelectric element 11 is projected toward the end surface (driver element surface) of the first elastic portion 101 of the rod-shaped elastic body 10.

  Thereby, if the unnecessary bending vibration component shown in FIG. 4, for example, is generated in the recess 9 of the first elastic portion 101 of the rod-shaped elastic body 10 in the torsional vibration frequency region, the unnecessary bending vibration component is set as the longitudinal vibration direction. It attenuates in the vertical direction and excites stable elliptical vibration on the end face of the first elastic part 101 of the rod-like elastic body 10.

  Further, the rod-shaped elastic body 10 has a proximal end of the rotating shaft 12 coaxially protruding at a substantially central portion of the end surface of the first elastic portion 101. A ring-shaped driver 13 made of, for example, a ceramic material or a resin material is attached to the end surface of the first elastic portion 101 of the rod-shaped elastic body 10.

  When an alternating voltage having a different phase is applied to the two laminated piezoelectric elements 11 to simultaneously excite longitudinal vibrations and torsional vibrations in the bar-shaped elastic body 10, the driver 13 generates unnecessary bending vibrations other than the longitudinal vibrations. Elliptical vibrations are excited with the components removed.

  The multilayer piezoelectric element 11 is formed of a high melting point conductive material such as silver palladium that can withstand the temperature at which the internal electrode is sintered, for example, by a technique such as screen printing, and has a thickness of about 10 to 200 μm. The piezoelectric material is laminated to a size of about 10 mm.

  Further, after the driven body 14 constituting the rotor is rotatably inserted into the rotary shaft 12, a spring member 15 and a spring pressing member 16 are sequentially inserted, and for example, a screw portion (see FIG. The nut member 17 is screwed to the not shown. Thereby, the driven body 14 adjusts the pressure contact force with respect to each contact surface of the two drive elements 13 by the spring pressing member 16 changing the spring force of the spring member 15 by adjusting the screwing of the nut member 17. Is done.

  In the above configuration, when an alternating voltage having a different phase is applied to the two laminated piezoelectric elements 11, the rod-shaped elastic body 10 is excited simultaneously with longitudinal vibration and torsional vibration, and elliptical vibration is generated in the driver 13. Excited. At this time, when the flexural vibration is generated in the torsional vibration frequency region, the bar-like elastic body 10 has its concave portion 9 exerts a vibration buffering action to reduce displacement due to the flexural vibration as shown in FIG. And longitudinal vibration resonance frequency.

  As a result, the driver element 13 disposed on the end face of the first elastic portion 101 of the rod-shaped elastic body 10 is excited by stable elliptic vibration without being affected by unnecessary bending vibration, and the elliptic vibration is used as a driving force. The driven body 14 arranged in pressure contact is rotationally driven with desired sliding characteristics. Thereby, highly efficient sliding characteristics can be obtained, and high motor efficiency can be obtained.

  As described above, the ultrasonic motor is provided with the concave portion 9 corresponding to the laminated piezoelectric element 11 on the side surface of the rod-shaped elastic body 10, and the concave portion 9 is unnecessary other than torsional vibration due to excitation of torsional vibration of the rod-shaped elastic body 10. The displacement due to the bending vibration is reduced, and the longitudinal vibration resonance frequency and the torsion vibration resonance frequency are matched.

  According to this, since the highly accurate and stable elliptical vibration can be excited on the driver 13 on the end surface of the first elastic portion 101 of the rod-like elastic body 10, a highly efficient sliding characteristic can be obtained. Efficiency can be improved.

  Moreover, although the said embodiment demonstrated the case where the recessed part 9 distribute | arranged to the 1st elastic part 101 of the rod-shaped elastic body 10 was comprised as one groove structure, this invention is not restricted to this, others, For example, as shown in FIGS. 6 to 10, the recesses 91 to 95 may be configured, and the same effect is expected. However, in each embodiment shown in FIGS. 6 to 10, the same components as those shown in FIGS. 1 to 5 are denoted by the same reference numerals, and detailed description thereof is omitted.

  The recess 91 shown in FIG. 6 is configured by arranging a plurality of grooves 911 in parallel with each other using a partition wall 912 with a width interval.

  The recess 92 shown in FIG. 7 is configured by arranging a plurality of grooves 921 in parallel with different width intervals using partition walls 922.

  The concave portion 93 shown in FIG. 8 is formed by arranging a plurality of grooves 931 in parallel at a predetermined width interval using, for example, partition walls 932 whose both surfaces are inclined in the distal direction and sharpened in the distal direction.

  The concave portion 94 shown in FIG. 9 is configured by arranging a plurality of grooves 941 in parallel at different width intervals using, for example, partition walls 942 whose both surfaces are inclined in the distal direction and sharpened in the distal direction.

  The concave portion 95 shown in FIG. 10 is configured by arranging a plurality of grooves 951 in parallel with different width intervals using partition walls 952 that are inclined in the tip direction, for example, only on one surface.

  10 may be applied to the partition walls 932 and 942 in the recesses 93 and 94 shown in FIG. 8 and FIG. 9 described above. .

  In each of the above embodiments, the case where the rod-like elastic body 10 is formed in a columnar shape has been described. However, the present invention is not limited to this, and the rod-like elastic body 10 can be formed in a prismatic shape and is also effective. Expected.

  Furthermore, the present invention is not limited to the above-described embodiment, and, for example, a rubber material or the like is provided in the concave portion 9 (91, 92, 93, 94, 95) formed in the first elastic portion 101 of the rod-shaped elastic body 10, for example. A vibration damping material having a buffer function such as a resin material may be embedded. According to this, a better buffering effect can be expected.

  Therefore, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention at the stage of implementation. Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the effect of the invention can be obtained. In such a case, a configuration in which this configuration requirement is deleted can be extracted as an invention.

It is the top view shown in order to demonstrate the principal part structure of the ultrasonic motor which concerns on one embodiment of this invention. It is the top view which showed the state which looked at FIG. 1 from the side surface side. It is the top view shown in order to demonstrate the longitudinal vibration and torsional vibration mode excited by the rod-shaped elastic body of FIG. It is the top view shown in order to demonstrate the bending vibration generate | occur | produced in the rod-shaped elastic body of FIG. It is the top view which expanded and showed the principal part in order to demonstrate the effect | action of the recessed part of FIG. It is the partial cross section figure which expanded and showed the principal part structure of the ultrasonic motor which concerns on other embodiment of this invention. It is the partial cross section figure which expanded and showed the principal part structure of the ultrasonic motor which concerns on other embodiment of this invention. It is the partial cross section figure which expanded and showed the principal part structure of the ultrasonic motor which concerns on other embodiment of this invention. It is the partial cross section figure which expanded and showed the principal part structure of the ultrasonic motor which concerns on other embodiment of this invention. It is the partial cross section figure which expanded and showed the principal part structure of the ultrasonic motor which concerns on other embodiment of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 9 ... Concave part 10 ... Rod-shaped elastic body 101 ... 1st elastic part 102 ... 2nd elastic part 103 ... Groove part, 11 ... Laminated piezoelectric element, 12 ... Rotary shaft, 13 ... Driver, 14 ... Covered Drive unit, 15 ... spring member, 16 ... spring pressing member, 17 ... nut member, 91, 92, 93, 94, 95 ... recess, 911, 921, 931, 941, 951 ... groove, 912, 922, 932, 942 , 952 ... Septum.

Claims (7)

The longitudinal vibration and the torsional vibration are excited in the rod-like elastic body by the stretching vibration of the two laminated piezoelectric elements arranged facing the side surfaces of the rod-like elastic body, and the drive provided on the end surface of the rod-like elastic body An ultrasonic motor that excites elliptical vibration in a child and frictionally drives a driven member that is rotatably supported on an end face of the rod-like elastic body with respect to the driver;
An ultrasonic motor characterized in that a vibration buffer portion is provided on a side surface of the rod-shaped elastic body so as to correspond to the laminated piezoelectric element.   2. The ultrasonic motor according to claim 1, wherein the vibration buffering portion is provided at a position including a region where the laminated piezoelectric element of the rod-shaped elastic body is projected toward a driver surface.   2. The ultrasonic motor according to claim 1, wherein the vibration buffer portion is provided in a region including an antinode of torsional vibration of the rod-like elastic body.   The ultrasonic motor according to claim 1, wherein the vibration buffer region is formed by one or more recesses.   The ultrasonic motor according to claim 1, wherein the vibration buffer portion has a plurality of recesses formed at equal intervals.   The ultrasonic motor according to claim 1, wherein the vibration buffer portion has a plurality of recesses formed at unequal intervals.   The ultrasonic motor according to any one of claims 4 to 6, wherein a vibration damping material is embedded in the concave portion constituting the vibration buffer portion.

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