Piezo ultrasonic motor having harmonic drive structure

Abstract

The present invention provides a piezo ultrasonic motor having a harmonic drive structure. The present invention provides a piezo ultrasonic motor comprising: a piezoelectric body including a plurality of piezoelectric elements which are polarized in opposite polarities in a circumferential direction around a rotation axis and are alternately arranged; a hollow stator which is attached to an upper part of the piezoelectric body and vibrates through a progressive wave generated when the piezoelectric body is expanded and contracted according to the application of an AC voltage; and a rotor which comes in contact with the stator and rotates according to the vibration of the stator, wherein a plurality of first teeth are formed on an upper portion of the stator and a plurality of second teeth different in number from the plurality of first teeth are formed on a lower portion of the rotor such that at least a portion of the plurality of first teeth is engaged with the plurality of second teeth according to the vibration of the stator and at least a portion of the rotor is engaged with the rotating first teeth.

Description

Piezoelectric ultrasonic motor with harmonic drive structure

[0001] The present invention relates to a piezoelectric ultrasonic motor having a harmonic drive structure.

[0002] A piezoelectric ultrasonic motor is a low-noise, high-torque motor that uses a piezoelectric material as a driving source that expands when voltage is applied.

[0003] Unlike general electromagnetic motors, it operates using frictional force rather than coils or magnets, so it is small and lightweight, can be used in magnetic field environments, and has the advantage of no backlash.

[0004] Piezoelectric ultrasonic motors are used as direct drive motors for positioning stages, belt conveyors, angle calculators, and posture control devices such as robot arms, and as motors for MRI and semiconductor manufacturing devices. In particular, as the use of robots increases, miniaturization and weight reduction are required.

[0005] In order to solve the problems of the above-mentioned prior art, the present invention proposes a piezo ultrasonic motor having a harmonic drive structure that can be miniaturized and lightweight.

[0006] In order to achieve the above object, according to one embodiment of the present invention, there is provided a piezoelectric ultrasonic motor including: a piezoelectric body having a plurality of piezoelectric elements polarized in opposite polarities in a circumferential direction centered on a rotational axis; a hollow ring-shaped stator attached to an upper portion of the piezoelectric body and vibrating through a traveling wave generated by the piezoelectric body expanding and contracting in response to an AC voltage application; and a rotor that contacts and rotates in response to vibration of the stator, wherein a plurality of first teeth are formed in a circumferential direction on an upper portion of the stator, and a plurality of second teeth, a number of which is different from the plurality of first teeth, are formed in a circumferential direction on a lower portion of the rotor, such that at least some of the plurality of first teeth mesh with the plurality of second teeth in response to vibration of the stator, and at least some of the first teeth mesh with the plurality of second teeth, thereby rotating the rotor.

[0007] When the period of the above-mentioned progressive wave is N, N+M first teeth can be formed on the upper part of the stator, and M second teeth can be formed on the lower part of the rotor.

[0008] The above stator may be defined as a flex spline of a harmonic drive, and the above rotor may be defined as a circular spline of a harmonic drive.

[0009] The tooth shapes of the first and second teeth can be designed based on the period of the traveling wave and the trajectories of the first and second teeth.

[0010] According to another aspect of the present invention, a piezoelectric ultrasonic motor is provided, including: a piezoelectric body having a plurality of piezoelectric elements alternately arranged in a circumferential direction with opposite polarities centered on a rotational axis; a hollow ring-shaped stator attached to an upper portion of the piezoelectric body and vibrating through a traveling wave generated by the piezoelectric body expanding and contracting in response to an AC voltage application, and functioning as a flex spline of a harmonic drive through a plurality of first teeth formed in a circumferential direction on an upper portion; and a rotor having a plurality of second teeth formed in a circumferential direction on a lower portion, rotating by contacting at least some of the plurality of first teeth in response to vibration of the stator, and functioning as a circular spline of the harmonic drive.

[0011] According to the present invention, there is an advantage in that a piezo ultrasonic motor can be made smaller and lighter by adopting a harmonic drive structure.

[0012] FIG. 1 is a drawing showing the configuration of a piezo ultrasonic motor having a harmonic drive structure according to a preferred embodiment of the present invention.

[0013] FIG. 2 is a diagram illustrating a driving process of a piezoelectric ultrasonic motor having a harmonic drive structure according to the present embodiment.

[0014] Figures 3 and 4 are drawings showing the tooth structure formed in the stator and rotor according to the present embodiment.

[0015] Fig. 5 is a drawing illustrating a driving process of a piezoelectric ultrasonic motor having a harmonic drive structure according to the present embodiment.

[0016] The present invention is susceptible to various modifications and embodiments. Specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, but rather to encompass all modifications, equivalents, and alternatives falling within the spirit and technical scope of the present invention.

[0017] The terminology used herein is merely used to describe specific embodiments and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprises" or "has" indicate the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0018] In addition, it is to be understood that the components of the embodiments described with reference to each drawing are not limited to the specific embodiments, but may be implemented to be included in other embodiments within the scope in which the technical idea of ​​the present invention is maintained, and that multiple embodiments may be re-implemented as a single integrated embodiment even if a separate description is omitted.

[0019] In addition, when describing with reference to the attached drawings, identical components will be assigned identical or related reference numerals regardless of the drawing reference numbers, and redundant descriptions thereof will be omitted. When describing the present invention, if a detailed description of a related known technology is judged to unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

[0020]

[0021] FIG. 1 is a drawing showing the configuration of a piezo ultrasonic motor according to a preferred embodiment of the present invention.

[0022] As illustrated in FIG. 1, the piezoelectric ultrasonic motor according to the present embodiment may include a stator (10) and a rotor (11).

[0023] The stator (10) is formed in a hollow ring shape and can be formed of a metal material having electrical conductivity, for example, steel such as stainless steel or bronze.

[0024] A piezoelectric element (12) is connected to the lower part of the stator (10) by a conductive adhesive such as epoxy.

[0025] The piezoelectric material (12) expands when an AC voltage is applied, and the stator (10) is deformed as shown in Fig. 2 by the N-cycle traveling wave generated by the expansion of the piezoelectric material (12).

[0026] More specifically, piezoelectric elements polarized with positive and negative poles may be alternately arranged along the circumference of the rotation axis. Each of the first and second piezoelectric elements may be formed as a hollow ceramic disk having a thin thickness, for example, tens to hundreds of microns in thickness, so that even when a low voltage is applied, micro-displacement or micro-deformation may occur due to the piezoelectric effect, thereby generating vibration.

[0027] The stator (10) vibrates due to the expansion and contraction of the piezoelectric material (12).

[0028] The stator (10) acts as an elastic ring, and the traveling wave causes the rotor (11) to perform an elliptical motion.

[0029] In a typical piezoelectric ultrasonic motor, a wear-resistant coating layer is formed on the upper part of the stator (10), and the rotor (11) is pushed and rotated through contact between the stator (10) and the rotor (11).

[0030] However, the present invention uses a harmonic driver structure in a piezo ultrasonic motor that rotates by frictional force, thereby realizing a desired reduction ratio and enabling miniaturization and weight reduction.

[0031] Figures 3 and 4 are drawings showing the tooth structure formed in the stator and rotor according to the present embodiment.

[0032] As shown in FIGS. 3 and 4, a plurality of first teeth (30) and second teeth (31) in different numbers are formed along the circumferential direction on the upper part of the stator (10) and the lower part of the rotor (11) according to the present embodiment.

[0033] The shape (tooth form) of the first and second teeth (30, 31) can be designed based on the traveling wave and the trajectory of the teeth.

[0034] FIG. 3 is a drawing showing a piezoelectric ultrasonic motor in which N+M first teeth (30) are formed on the upper part of a stator (10) that vibrates according to a traveling wave of N cycles, and M second teeth (31) are formed on the lower part of a rotor (10) so that the reduction ratio becomes M / N.

[0035] Here, the stator (10) having N+M first teeth (30) formed can be defined as a flexspline of a harmonic drive, and the rotor (11) having M second teeth (31) formed can be defined as a circularspline of a harmonic drive.

[0036] As shown in Fig. 3, a higher torque can be obtained by forming the number of teeth formed on the upper part of the stator (10) and the lower part of the rotor (11) differently.

[0037] Meanwhile, FIG. 4 is a drawing showing a case where the number of teeth formed on the upper part of the stator (10) is greater than the number of teeth formed on the lower part of the rotor (11).

[0038] According to this embodiment, various reduction ratios can be obtained by forming different numbers of teeth in the stator (10) and the rotor (11).

[0039] Fig. 5 is a drawing illustrating a driving process of a piezoelectric ultrasonic motor having a harmonic drive structure according to the present embodiment.

[0040] As illustrated in FIG. 5, the piezoelectric ultrasonic motor according to the present embodiment rotates the rotor (11) as the teeth (30) formed on the upper portion of the stator (10) and some of the teeth (31) arranged on the lower portion of the rotor (11) engage with each other in response to the vibration of the stator (10).

[0041] The above-described embodiments of the present invention are disclosed for the purpose of illustration, and those skilled in the art with common knowledge of the present invention will be able to make various modifications, changes, and additions within the spirit and scope of the present invention, and such modifications, changes, and additions should be considered to fall within the scope of the following patent claims.

Claims

1. A piezoelectric material in which a plurality of piezoelectric elements polarized with opposite polarities are alternately arranged along the circumference around a rotation axis; A hollow ring-shaped stator attached to the upper part of the piezoelectric body and vibrating through a traveling wave generated by the piezoelectric body expanding and contracting according to the application of an AC voltage; and Including a rotor that rotates by contacting with the vibration of the stator, A piezoelectric ultrasonic motor in which a plurality of first teeth are formed along a circumferential direction on an upper portion of the stator, and a plurality of second teeth, a number of which is different from the plurality of first teeth, are formed along a circumferential direction on a lower portion of the rotor, such that at least some of the plurality of first teeth mesh with the plurality of second teeth according to vibration of the stator, and at least some of the first teeth mesh with the plurality of second teeth, thereby rotating the rotor.

2. In paragraph 1, A piezoelectric ultrasonic motor in which, when the period of the above-mentioned forward wave is N, N+M first teeth are formed on the upper part of the stator, and M second teeth are formed on the lower part of the rotor.

3. In paragraph 1, A piezoelectric ultrasonic motor wherein the stator is defined by a flex spline of a harmonic drive and the rotor is defined by a circular spline of a harmonic drive.

4. In paragraph 1, A piezoelectric ultrasonic motor in which the tooth shapes of the first and second teeth are designed based on the period of the traveling wave and the trajectories of the first and second teeth.

5. A piezoelectric material in which a plurality of piezoelectric elements polarized with opposite polarities are alternately arranged along the circumference around the rotation axis; A hollow ring-shaped stator attached to the upper portion of the piezoelectric body, vibrating through a traveling wave generated by the piezoelectric body expanding and contracting according to the application of an alternating voltage, and functioning as a flex spline of a harmonic drive through a plurality of first teeth formed along the circumferential direction on the upper portion; and A piezoelectric ultrasonic motor comprising a rotor having a plurality of second teeth formed along a circumferential direction at the bottom and rotating in contact with at least some of the plurality of first teeth according to vibration of the stator, and functioning as a circular spline of a harmonic drive.

6. In paragraph 5, A piezoelectric ultrasonic motor in which, when the period of the above-mentioned forward wave is N, N+M first teeth are formed on the upper part of the stator, and M second teeth are formed on the lower part of the rotor.

7. In paragraph 5, A piezoelectric ultrasonic motor in which the tooth shapes of the first and second teeth are designed based on the period of the traveling wave and the trajectories of the first and second teeth.

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