KR20100079938A - Piezo motor and lens assembly having the same - Google Patents

Abstract

PURPOSE: A piezoelectric motor and a lens assembly thereof are provided to improve abrasion resistance and durability by alleviating stress concentration between a rotor and a stator. CONSTITUTION: A piezoelectric motor comprises a stator(10) and a rotor(20). A piezoelectric element(30) is combined in the first surface of the stator. A plurality of supporting protrusions(15) are formed on the second surface of the stator. A curved part is formed in the top surface and the contact part of the supporting protrusion. The rotor is compressed to the surface of the stator. The rotor revolves along the bending wave of the stator.

Description

Piezo motor and lens assembly having same {Piezo motor and lens assembly having the same}

The present invention relates to a piezoelectric motor and a lens assembly having the same, and more particularly, to a piezoelectric motor and a lens assembly having the same, which have improved wear resistance, which has a long service life and minimizes a loss in power transmission.

In general, a piezoelectric motor refers to a motor having a driving force by friction of a stator and a rotor while the driving frequency has ultrasonic waves (20 kHz or more). Piezoelectric motors are a new type of driving source that does not require magnets or windings. The principle of operation is to use a plurality of piezoelectric ceramics and apply high frequency voltage to them to vibrate the piezoelectric ceramics. In this vibration force, a driving force in a predetermined direction, that is, a rotational force, is obtained through the elastic body and the friction plate. According to a specific embodiment of the piezoelectric motor, in addition to the rotary type, there is a straight type (linear drive type). However, such a piezoelectric motor generates a driving force by the friction action between the stator as the stator and the rotor as the rotor, and thus has a disadvantage of being vulnerable to frictional wear.

An object of the present invention relates to a piezoelectric motor and a lens assembly having the same, which has improved wear resistance, which has a long service life and minimizes a loss in power transmission.

In order to achieve the above and other objects, the piezoelectric motor of the present invention includes a first surface and a plurality of supporting protrusions, each of which includes a piezoelectric element for inducing a bending wave as a driving signal is applied. A stator having a face; And

And a rotor which is pressed in contact with the support protrusion and driven to rotate according to the bending wave of the stator.

A rounded curved portion is formed at an edge portion that meets the pressing contact surface of the support protrusion.

When the support protrusion has a top surface in contact with the rotor, and both sides spaced apart from the adjacent support protrusions at regular intervals, the curved portion may be formed at the corner portion where the top surface and the side of the support protrusion meet.

On the other hand, the lens assembly according to another aspect of the present invention,

A stator having a first surface coupled with a piezoelectric element inducing a bending wave as a driving signal is applied, and a second surface on which a plurality of support protrusions are formed;

A rotor that is in pressure contact with the support protrusion and is driven to rotate in accordance with the bending wave of the stator; And

And at least one lens connected to the rotor and movably mounted according to the rotation state of the rotor.

A rounded curved portion is formed at an edge portion that meets the pressing contact surface of the support protrusion.

On the other hand, the piezoelectric motor according to another aspect of the present invention,

A stator having a first surface coupled with a piezoelectric element inducing a bending wave as a driving signal is applied, and a second surface on which a plurality of support protrusions are formed; And

And a rotor which is pressed in contact with the support protrusion and driven to rotate according to the bending wave of the stator.

At least one notch is formed on a side surface of the support protrusion protruding from the stator to the rotor side.

For example, the notch portion is opened in a semicircular shape toward the lateral direction. In this case, when the notch portion has a semicircle shape having a diameter D centered at a position L at a distance from the contact surface with the rotor, the notch portion may be designed to satisfy a relationship of L / D ≦ 1.5.

Further, the diameter D of the notched portion and the width W of the support protrusion may be designed to satisfy the relationship of D / W ≦ 0.2.

The notch may be formed on both left and right sides of the support protrusion.

Lens assembly according to another aspect of the present invention,

A stator having a first surface coupled with a piezoelectric element inducing a bending wave as a driving signal is applied, and a second surface on which a plurality of support protrusions are formed;

A rotor that is in pressure contact with the support protrusion and is driven to rotate in accordance with the bending wave of the stator; And

And at least one lens connected to the rotor and movably mounted according to the rotation state of the rotor.

At least one notch is formed on a side surface of the support protrusion protruding from the stator to the rotor side.

According to the present invention, by reducing stress concentration between the stator and the rotor constituting the main portion of the piezoelectric motor, the wear resistance can be improved and the durability life of the piezoelectric motor can be extended. In addition, by extending the contact surface between the stator and the rotor, it is possible to minimize the power loss that does not contribute to rotation due to local sliding and to increase the driving efficiency.

Hereinafter, a piezoelectric motor and a lens assembly having the same according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings. 1 is an exploded perspective view of a piezoelectric motor according to an exemplary embodiment of the present invention, and FIGS. 2 and 3 are views for explaining a driving principle of a piezoelectric motor. Referring to the drawings, the piezoelectric motor includes an annular stator 10 in which a plurality of support protrusions are formed by dividing the circumferential phase, and a rotor 20 that is pressed onto the surface of the stator 10.

The stator 10 and the rotor 20 are in pressure contact with a predetermined pressure, and the bending vibration of the stator 10 is converted into the rotational motion of the rotor 20 by the friction action induced at the contact surface. The stator 10 generates a bending wave that travels along an annular circumference, and the progressive bending wave rotates the rotor 20 by pushing the rotor 20 in one rotational direction through the contact surface.

For example, the stator 10 may be formed of a metallic elastic material, and may be formed of an aluminum-based or copper-based soft metal material. The stator 10 includes a stator body 11 formed in an annular shape, and a plurality of support protrusions 15 formed at regular intervals along the circumference of the body 11. The support protrusions 15 protrude toward the rotor 20 to form a contact friction surface between the rotor 20 and the stator 10. The support protrusions 15 serve to amplify the progressive bending wave generated by the piezoelectric element 30, and each of the support protrusions 15 follows an elliptical motion trajectory. That is, the support protrusion 15 participating in the progressive bending wave follows the elliptical motion trajectory, and each of the support protrusions 15 and the points of the support protrusion 15 having a position difference with each other has a phase difference from each other and has an elliptical motion trajectory. By following this, a continuous bending wave is formed (see FIG. 7).

The rotor 20 includes a rotor body 21 formed in an annular shape and a flange portion 25 extending in the circumferential direction from the rotor body 21. The flange portion 25 is formed with a relatively thin thickness and provides a low rigidity suitable for flexible deformation along the bending waveform of the stator 10. The flexible deformation of the rotor 20 allows the contact surface with the stator 10 to be enlarged and maintained stably, thereby preventing loss of power transmission and reducing frictional wear between parts.

The stator 10 is in intimate contact with the piezoelectric element 30 excited by the high frequency drive signal. The stator 10 is vibrated by the wave of the bending traveling wave by the piezoelectric element 30 formed below. For example, the piezoelectric element 30 generates a curved traveling wave in the stator 10 by inputting a voltage signal having a periodic waveform, for example, a voltage signal having a periodic sinusoidal waveform. The piezoelectric element 30 may be formed of a piezoelectric ceramic.

4 is a perspective view illustrating main parts of the main part of the stator 10 illustrated in FIG. 1. Referring to the drawings, a plurality of support protrusions 15 are formed on the stator main body 11 protruding at regular intervals d. Each of the supporting protrusions 15 may have a substantially rectangular shape including an upper surface 15U facing the rotor 20 and side surfaces 15S on both sides. At this time, a rounded curved portion 15R is formed at the corner portion where the upper surface 15U and the side surface 15S of the support protrusion 15 meet. The curved portion 15R is designed for reducing the frictional wear by reducing stress concentrated at the corners, as well as for reducing the wear of the other rotor 20 which is in contact with the edges, thereby extending the overall durability of the piezoelectric motor. will be. In addition, by enlarging the contact surface with the rotor 10, the effect of reducing the loss on power transmission and preventing local slippage can also be achieved.

The effect obtained by designing the rounded curved portion 15R on the support protrusion 15 can be clearly understood through contrast with the comparative example shown in FIGS. 5 to 7. Fig. 5 is a perspective view showing the main portion of the stator 10 'employed in the comparative example. The illustrated stator 10 'has a stator main body 11' formed in a ring shape and supporting protrusions 15 'protruding from the main body 11'. Each support protrusion 15` has an upper surface 15U` that is in contact with the rotor and side surfaces 15S` on both the left and right sides, and an edge portion where the upper surface 15U` and the side surface 15S` meet is an angled shape ( E)

6 is a view showing a contact state between the stator 10 'and the rotor 20'. Referring to the drawings, a contact is generated between the support protrusions 15` and the rotor 20` forming a top along a bending wave induced in the stator 10`, and a stator 10` for power transmission. Contact between the rotors 20 'is limited to the local area of some support protrusions 15'. FIG. 6 shows the distribution of stress p of the support protrusion 15 ′ which contacts the rotor 20 ′ and provides the driving force. The support protrusion 15 ′ positioned at the top portion of the bending wave may maintain contact with the rotor 20 ′ through the entire upper surface. At this time, when looking at the distribution of the stress (p), intensive stress (Stress Singularity) is generated on the left and right sides of the support protrusion (15`), the stress concentrated on the edge portion of the support protrusion (15`), as well as the other side It also promotes wear of the inverter 20 'and shortens the durability life of the piezoelectric motor.

FIG. 7 is a view showing the motion trajectory F of the support protrusion 15 ′. Referring to the drawings, the support protrusion 15 ′ participating in the progressive bending wave follows the elliptical motion trajectory F, and each point having a position difference from each other has a phase difference from each other and follows the elliptical motion trajectory F. This results in a continuous bending wave.

The tangential direction on the elliptical motion trajectory F represents the instantaneous velocity vector, and as shown, the instantaneous velocity at each point is different from each other. The movement observed in each support protrusion 15 'also has a rotational component along with the translational component in the vertical direction. For example, as shown, the central support protrusion 15`-1 in the parallel movement section takes a vertical posture, but the support protrusions 15`-2 and 15 on both sides in the falling section and the rising section. `-3) will be inclined at an oblique angle.

As shown, the central support protrusion 15`-1 in the parallel movement section is in contact with the rotor 20`through almost the entire surface of the upper surface 15U`, but the support protrusion 15`- in the ascending section. 2) are in contact with the rotor 20` through the local area of the left edge CL, and the supporting projections 15`-3 in the lowering section are located in the rotor 20` through the local area of the right edge CR. ). Therefore, both edge portions CL, CR of the support protrusions 15`-2, 15`-3 are vulnerable to frictional wear due to pressure contact with the rotor 20`, and the wear degree of the other rotor 20 'is also reduced. Will be accelerated. In addition, as described with reference to FIG. 6, stress concentrations appear on both left and right sides of the support protrusion 15 ′-1, which forms a surface contact through the entire upper surface 15 U ′.

As shown in FIG. 4, by designing the rounded curved portion 15R at the corners of the support protrusions 15 forming the friction driving surface with the rotor 20, not only the stress concentration at the edges but also the edges are reduced. The durability of the piezoelectric motor as a whole can be extended by alleviating the wear of the counterpart rotor 20 that is pressed against the portion. In addition, the support protrusions 15 participating in the progressive bending wave follow the elliptical motion trajectory F to transmit the rotational force to the rotor 20 through the corner portion of the support protrusion 15 according to the phase state. At this time, by designing the rounded curved portion 15R at the corner portion, the friction driving surface can be enlarged, and the driving loss (ex. Sliding, etc.) generated during the power transmission process between the stator 10 and the rotor 20 is minimized. You can.

8 is a vertical cross-sectional view of the lens assembly 50 according to another aspect of the present invention, a vertical cross-sectional view of the lens assembly 50 to which the piezoelectric motor of FIG. 1 is applied. For example, the lens assembly 50 performs a zooming operation between the wide position and the tele position by driving at least one optical lens 40 along the optical axis direction C. It can be a lens barrel or form part of it.

Referring to the drawings, the lens assembly 50 has a fixing frame 51 and a lens support portion 41 operably installed in the optical axis direction C inside the fixing frame 51, and the lens support portion 41 It includes an optical lens 40 mounted on). A support body 55 is fixed to the flange portion 51a of the fixed frame 51, and a stator 10 having the piezoelectric element 30 mounted thereon is mounted therebetween. According to the driving signal applied to the piezoelectric element 30, the progressive bending wave generated in the stator 10 is transmitted to the rotor 20. The rotational movement of the rotor 20 is converted into a straight movement (regression movement) along the optical axis direction C by a cam-follower mechanism that mediates power transmission between the rotor 20 and the lens support 41. do.

The cam follower mechanism includes a straight guide slit 20 'formed in the rotor 20 and a curved cam slit formed in the fixed frame 51 corresponding to the straight guide slit 20'. 51 '), and a driving pin 45 that is assembled to the lens support part 41 through the guide slit 20' and the cam slit 51 '.

When a high frequency voltage is applied to the piezoelectric element 30, a progressive bending wave is generated in the stator 10, and the rotor 20 which is pressed against the stator 10 rotates. As the rotor rotates, the driving pin 45 is forced by the guide slit 20 'while following the cam slit 51', and moves back and forth along the optical axis direction C simultaneously with the rotation. At this time, the lens support 41 is integrally driven together with the driving pin 45 so that the optical lens 40 moves in the optical axis direction C and implements a zoom operation.

FIG. 9 is a perspective view showing a main portion of a stator 110 applied to a piezoelectric motor according to a second embodiment of the present invention. Referring to the drawings, the stator 110 includes a stator main body 111 having an annular edge shape and a plurality of supporting protrusions 115 protruding at a predetermined distance d on the stator main body 111. do. A rounded curved portion 115R may be formed at an edge portion where the upper surface 115U and the side surface 115S of the stator facing the rotor meet. On the other hand, notches 115 ′ of a symmetrical form are formed on both side surfaces 115S of each of the support protrusions 115. For example, each notch 115 ′ may be formed in a semicircle shape having a constant radius, and may be formed at a constant height from the upper surface 115U.

As shown in FIG. 6, stress support is concentrated on the left and right edges of the support protrusion 115 compressed to the rotor. The notch 115 ′ designed on the support protrusion 115 has the purpose of relieving stress concentrated at the edge and dispersing the stress in the entire cross section of the support protrusion 115.

Since the shape and position of the notch 115 'are directly related to the stress relaxation effect, it is preferable that the notch 115' be designed within an appropriate range. As shown in FIG. 10, when the notch portion 115 ′ is formed in a semicircular shape having a centrifugal position at a position separated by L from the contact surface with the rotor 20 to the upper surface 115U and having a diameter D, the distance L The design variable N, which is defined as the relative ratio between the and diameter D, preferably satisfies N = L / D ≦ 1.5. This is based on the result of calculating the stress distribution while fixing the diameter D and changing the distance L to the center of the notch part 115`. When the distance L increases beyond the upper limit 1.5, that is, the notch part 115` contacts. This is because the stress relaxation effect is drastically dropped when it is excessively far from the surface 115U.

On the other hand, since the pressure exerted by the rotor 20 is concentrated on the neck portion between the notches 115 ', the diameter D of the notches 115' is designed such that D / W ≤ 0.2 in relation to the width W of the supporting protrusion. It is desirable to be. This takes into account the stress concentration in the neck which may be caused by overdesigning the notch diameter D.

Although the present invention has been described with reference to the embodiments illustrated in the accompanying drawings, this is merely exemplary, and various modifications and equivalent other embodiments may be made by those skilled in the art to which the present invention pertains. You can understand that.

1 is an exploded perspective view of a piezoelectric motor according to an embodiment of the present invention.

2 and 3 are diagrams for explaining the driving principle of the piezoelectric motor.

4 is an enlarged perspective view illustrating a main part of the piezoelectric motor illustrated in FIG. 1.

5 is a perspective view showing a main part of a piezoelectric motor according to a comparative example compared with the present invention.

FIG. 6 is a diagram illustrating a stress distribution acting on the support protrusion illustrated in FIG. 5.

7 is a view showing an elliptical motion trajectory of the stator.

8 is a vertical cross-sectional view of the lens assembly to which the piezoelectric motor shown in FIG. 1 is applied.

9 is a perspective view showing a main part of a piezoelectric motor according to a second embodiment of the present invention.

10 is a view showing in more detail the shape of the support protrusion shown in FIG.

<Explanation of symbols for the main parts of the drawings>

10,110: Stator 11,111: Stator body

15,115 support protrusion 15U, 115U: top surface of support protrusion

15S, 115S: Side surface of support protrusion 15R, 115R: Curved part

20: rotor 20`: guide slit

30 piezoelectric element 40 optical lens

41: lens support 45: drive pin

50 lens assembly 51 fixed frame

51`: cam slit 55: support

115`: notch

Claims (9)

A stator having a first surface coupled with a piezoelectric element inducing a bending wave as a driving signal is applied, and a second surface on which a plurality of support protrusions are formed; And And a rotor which is pressed in contact with the support protrusion and driven to rotate according to the bending wave of the stator. Piezoelectric motor, characterized in that the rounded curved portion is formed in the corner portion that meets the pressing contact surface of the support projection. The method of claim 1, The support protrusion has an upper surface in contact with the rotor, and the sides of both sides spaced apart from the neighboring support protrusion at regular intervals, The curved portion is a piezoelectric motor, characterized in that formed on the corner portion where the upper surface and the side of the support protrusion meet. A stator having a first surface coupled with a piezoelectric element inducing a bending wave as a driving signal is applied, and a second surface on which a plurality of support protrusions are formed; A rotor that is in pressure contact with the support protrusion and is driven to rotate in accordance with the bending wave of the stator; And And at least one lens connected to the rotor and movably mounted according to the rotation state of the rotor. A lens assembly, characterized in that the rounded curved portion formed in the corner portion that meets the pressing contact surface of the support projection. A stator having a first surface coupled with a piezoelectric element inducing a bending wave as a driving signal is applied, and a second surface on which a plurality of support protrusions are formed; And And a rotor which is pressed in contact with the support protrusion and driven to rotate according to the bending wave of the stator. At least one notch is formed on the side surface of the support protrusion protruding from the stator to the rotor side. The method of claim 4, wherein And the notch portion is opened in a semicircular shape toward the lateral direction. The method of claim 5, And the notch portion is designed to satisfy a relationship of L / D ≤ 1.5 when the notch portion has a semicircle shape having a diameter D centered at a position L from a contact surface with the rotor. The method of claim 5, A diameter D of the notch portion and a width W of the support protrusion are designed to satisfy a relationship of D / W ≤ 0.2. The method of claim 4, wherein The notch part is formed on the left and right sides of the support projection piezoelectric motor. A stator having a first surface coupled with a piezoelectric element inducing a bending wave as a driving signal is applied, and a second surface on which a plurality of support protrusions are formed; A rotor that is in pressure contact with the support protrusion and is driven to rotate in accordance with the bending wave of the stator; And And at least one lens connected to the rotor and movably mounted according to the rotation state of the rotor. At least one notch is formed on a side surface of the support protrusion protruding from the stator to the rotor side.

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