JPH0654558A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To provide an ultrasonic motor having a high efficiency in which an ultrasonic vibrator is securely supported without almost causing the vibration loss. CONSTITUTION:At ultrasonic motor comprises an ultrasonic vibrator 8 in which a bending vibration rotation around a center shaft is generated by applying sine-wave voltage with their phases shifted 90 deg. each other to first and second piezoelectric elements 1 and 2 installed with their positions shifted 90 deg., a rotor 18 installed on either of one end of the ultrasonic vibrator 8, and a fine protrusion 15a installed in the proximity of the center shaft of a node position of the bending vibration generated on the ultrasonic vibration 8 and being in contact with an external fixing member 17 on a fine area.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor, and more particularly to an ultrasonic motor which rotates by utilizing the vibration generated by a vibration generating means.

[0002]

2. Description of the Related Art Conventionally, in Japanese Patent Application Laid-Open No. 4-91671, a supporting member having elasticity is provided at one end or both ends of a fastening member that fastens each constituent member of an ultrasonic transducer, and the vibrator is provided. Technical means for supporting the body have been proposed. With this technical means, the frequency of the eigenmode under the boundary condition of the support member is set so that the driving frequency of the ultrasonic transducer is different. Further, by using such a supporting member, the supporting member follows the vibration displacement of the vibrator due to its elastic deformation, and no friction loss occurs, thereby improving the motor efficiency.

[0003]

However, the above-mentioned conventional supporting method is a very effective means for reducing the friction loss between the supporting member and the fixed member, but the supporting member is elastic. Therefore, there is a drawback that the support becomes unstable. In addition, since the stress of the ultrasonic vibration of the bending vibration is concentrated on the support member, there is a risk of breaking.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a high-efficiency ultrasonic motor in which an ultrasonic vibrator is supported firmly and with almost no vibration loss. And

[0005]

In order to achieve the above-mentioned object, the first ultrasonic motor according to the present invention comprises first and second electric motors, which are arranged with a positional offset of 90 °.
An ultrasonic transducer that generates bending vibrations that rotate around a central axis by applying sinusoidal voltages whose phases are shifted by 90 ° to each other to a mechanical energy conversion element, and is arranged on either end face of this ultrasonic transducer. And a micro-projection provided in the vicinity of the central axis at the node position of the bending vibration generated on the ultrasonic transducer and in contact with an external fixing member in a micro area. .

In order to achieve the above-mentioned object, the second ultrasonic motor according to the present invention has the first and second electro-mechanical energy conversion elements, which are arranged 90 ° apart from each other, in phase with each other. An ultrasonic transducer that generates a bending vibration that rotates about a central axis by applying a sine wave voltage that is deviated by 90 °, a driven member that is disposed on one end face of the ultrasonic transducer, The resonator is provided at the node position of the bending vibration generated on the ultrasonic vibrator, and is made of a material having a low vibration transmission speed.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view (a) of an ultrasonic motor according to a first embodiment of the present invention, and (b) a diagram showing a vibrating state.

As shown in FIG. 1 (a), this ultrasonic motor includes a first piezoelectric element 1 and a second piezoelectric element 2 which are arranged between three electrode plates 3, 4 and 5, respectively. , The first and second
The first resonator 6 and the second resonator 15 are arranged so as to sandwich the piezoelectric elements 1 and 2 between the end faces thereof, and the fastening member 9 that integrally fastens these constituent members in the axial direction. Ultrasonic transducer 8 and one end surface (upper end surface) of the ultrasonic transducer 8
The main part is constituted by a rotor 18 which is a driven member that is pressed into contact with and is rotated in a predetermined direction by the ultrasonic vibration of the ultrasonic vibrator 8.

The first and second piezoelectric elements 1 and 2 are shown in FIG.
As shown in the enlarged perspective view showing the polarization state of the piezoelectric element, the piezoelectric element has a disk shape having a hollow circular portion, and the polarization boundary lines 1a and 2a passing through the centers of the piezoelectric elements are provided as shown by arrows M1 and M2 in FIG. It is polarized in the opposite direction. The first piezoelectric element 1 and the second piezoelectric element 2 are arranged in the stacking direction such that their polarization boundary lines 1a and 2a are deviated from each other by 90 °.

The electrode plates 3, 4, and 5 have the first and second electrode plates.
Of the piezoelectric elements 1 and 2 are copper electrode plates for voltage application having a diameter substantially the same as that of the piezoelectric elements 1 and 2 and terminals A, G and B for lead wire soldering are respectively provided in a protruding manner and connected to a power source (not shown). ing. The first and second piezoelectric elements 1 and 2 and the electrode plates 3, 4, and 5 constitute a vibration generator 13.

FIG. 3 is an external perspective view showing the first resonator 6.

The first resonator 6 has a hollow cylindrical shape having a bottom portion 6b and is made of a material excellent in vibration transmission, for example, aluminum alloy, stainless steel, phosphor bronze, duralumin, titanium alloy. SUS4 in the example
40 C is heat treated to have a hardness of Hv 800 or more. In addition, in this embodiment, the first resonator 6 is formed by applying an oxalic acid alumite coating on an aluminum alloy,
Furthermore, the micropores of the alumite are filled up to the bottom with hydrate by a vapor sealing treatment.

At the center of the bottom portion 6b of the first resonator 6, a screw portion 9a screwed on the fastening member 9 (see FIG. 1).
A threaded portion 6 c that is screwed with is provided, and is screwed with the fastening member 9. Further, the inside of the first resonator 6 above the bottom portion 6b is a cup-shaped hollow portion 10 forming an opening at the upper end surface, and the upper end surface of the first resonator 6 is formed. Vibration is not regulated by the fastening member 9. Further, the upper portion 6 of the first resonator 6
A plurality of vertical grooves 11 are formed in the vertical direction on the outer peripheral side surface of the a, and the resonator upper part 6a is vertically divided into eight parts to contribute to vibration expansion. Further, a peripheral groove 14 is formed toward the center on the outer peripheral side surface between the resonator upper portion 6a and the resonator bottom portion 6b.

Below the first and second piezoelectric elements 1 and 2, a second resonator 15 having a contact surface of substantially the same size as the piezoelectric elements 1 and 2 is arranged. Second resonator 1
The electrode plate 3, 4, 5 and the first and second piezoelectric elements 1, 2 are sandwiched between 5 and the first resonator 6. The second resonator 15 is made of a material having a vibration transmission characteristic inferior to that of the first resonator 6, for example, brass or steel. In this embodiment, S45C is used.

FIG. 4 is an enlarged sectional view of an essential part showing an enlarged contact portion between the second resonator 15 and the external fixing portion 17.

As shown in this figure, the second resonator 15
The lower portion has a substantially conical shape in which a taper 16 is formed downward, and the tip portion 15a of the substantially conical portion is in line contact with the external fixing portion 17 as shown in FIG.

The electrode plate 3 and the first resonator 6 are also provided.
A disk-shaped insulating member having a hollow circular portion made of alumina, for example, is provided between the electrode plate 5 and the second resonator 15.

The ultrasonic oscillator 8 includes the first and second piezoelectric elements 1 and 2, the electrode plates 3, 4, 5 and the first resonator 6,
1 is laminated as shown in FIG. 1, an epoxy-based adhesive is applied between the respective constituent members, and then the fastening member 9 is penetrated through the center to pressure-bond each constituent member to cure the adhesive. It

On the other hand, bolts are formed on the fastening member 9 below the second resonator 15. The fastening member 9 press-bonds the ultrasonic transducer 8 above the second resonator 15 and supports the rotor 18, and the ultrasonic wave below the second resonator 15 is supported by the fastening member 9. The ultrasonic motor is fixed by crimping and supporting the lower end surface of the vibrator 8 on the fixing member 17.

The upper end surface of the first resonator 6, that is,
A rotor 18 that rotates in a predetermined direction by the ultrasonic vibration of the ultrasonic vibrator 8 is provided on the upper end surface of the ultrasonic vibrator 8 while being axially supported by the fastening member 9 via a plurality of bearings 19. There is. In addition, the ultrasonic transducer 8 of the rotor 18
A pressing mechanism composed of a leaf spring 21, a spring pedestal 20, and a nut 22 pivotally supported by the fastening member 9 is provided on the side opposite to the contact surface with the rotating member 18 so that the crimping force of the rotor 18 can be varied. Has become. The rotor 18 is made of, for example, an aluminum alloy, and its surface is subjected to oxalic acid alumite treatment.

In the ultrasonic motor constructed as described above, a sine wave voltage near the resonance frequency is applied to the terminals A and B of the electrode plates 3 and 5 with a time shift of 90 °, and the terminals of the electrode plate 4 are applied. By grounding G, the ultrasonic vibrator 8 causes a bending vibration of a first mode to rotate around the central axis of the vibrator 8, and the rotor 18 rotates in a predetermined direction.

Next, the operation of the ultrasonic motor of the first embodiment will be described.

FIG. 1B is a diagram showing the vibrating state of the ultrasonic motor of the first embodiment.

When a sine wave voltage with a 90 ° phase shift is applied to the ultrasonic motor of the first embodiment, the tip end portion 15a of the ultrasonic oscillator 8 is a fixed end.
A bending vibration of a first-order mode in which the fixed end is a node and the other end surface (upper end surface) of the ultrasonic transducer 8 is an antinode is generated as an elliptical vibration rotating about a central axis. This elliptical vibration causes the rotor 18 pressed by the ultrasonic vibrator 8 to rotate. When the phase difference between the two sine wave voltages is shifted by 180 °, the rotation direction of the elliptical vibration is reversed and the rotor 18 rotates in the opposite direction.

As described above, the resonator upper portion 6a has a vibration generating portion formed by the circumferential groove 14 formed along the circumferential direction on the outer peripheral side surface and the plurality of vertical grooves 11 formed substantially parallel to the central axis. A displacement magnifying effect of converting the vibration obtained from 13 into a large bending vibration is provided.

In the ultrasonic motor of this embodiment, due to the bending vibration of the first-order mode described above, the amplitude in the Y direction in the figure in the vibration generating section becomes almost zero, so that
The second piezoelectric elements 1 and 2 are arranged at the node positions, and the force coefficient (N / v) is improved. In addition, the tip 1
Since 5a is formed close to the central axis, the amplitude in the Y direction can be made almost zero, and the loss due to friction is reduced. Similarly, since the contact area between the tip portion 15a and the external fixing portion 17 is extremely small, bending vibration is not transmitted to the external fixing portion 17, and vibration loss is suppressed as much as possible.

Further, the second resonator 15 is replaced by the first resonator 6
By using a material whose vibration transmission speed is slower than
Vibration on the side of the second resonator 15 is suppressed to facilitate formation of a vibration node. Then, the vibration of the vibrator is mainly directed to the first resonator 6 side, and the strong vibration is transmitted to the first resonator 6. This makes it possible to obtain large-amplitude vibration close to the free vibration state without reducing the mechanical Qm of the ultrasonic vibrator generated by the support.

According to the first embodiment as described above, the large-amplitude vibration generated by the displacement magnifying effect is maintained, and a high mechanical Qm can be obtained. Therefore, the loss of vibration is eliminated and a highly efficient ultrasonic motor can be obtained. Further, since the supported portion is composed of the fastening member 9 and the tip end portion 15a of the lower end portion of the ultrasonic transducer 8, it is possible to form a very robust support portion having no elasticity. The sonic motor can be reliably supported.

Next, a second embodiment of the present invention will be described.

FIG. 5 is a sectional view (a) of an ultrasonic motor according to a second embodiment of the present invention, and (b) a diagram showing a vibrating state.

The basic structure of the second embodiment is the same as that of the first embodiment, and therefore only the different points will be described.

The first resonator 23 disposed above the first and second piezoelectric elements 1 and 2 in the ultrasonic transducer 27 is
Basically, it is a hollow cylindrical shape having a bottom portion 23b, which has a shape similar to that of the first resonator 6 in the first embodiment. The inside of the first resonator 23 above the bottom portion 23b is a cup-shaped hollow portion that forms an opening at the upper end surface, and vibrations at the upper end surface of the first resonator 23 occur. Are not regulated by the fastening member 9. Further, a plurality of vertical grooves 11 are formed on the outer peripheral side surface of the upper portion 23a of the first resonator 23 in the same manner as in the first embodiment, and the resonator upper portion 23a is vibrated by dividing the upper portion 23a into eight vertical portions. Contributes to expansion. Further, on the outer peripheral side surface between the resonator upper portion 23a and the resonator bottom portion 23b, a peripheral groove 26 having a trapezoidal cross section toward the center direction is formed.
Are formed.

On the other hand, below the second resonator 15 arranged below the first and second piezoelectric elements 1 and 2,
A crimp nut 28 is arranged as shown in the drawing, and the first and second piezoelectric elements 1 and 2 and the second resonator 15 are
It is configured to be sandwiched between the first resonator 23 and the crimp nut 28.

FIG. 6 is an enlarged cross-sectional view of an essential part showing a contact portion between the crimp nut 28 and the external fixing portion 17.

As shown in this figure, a minute projection portion 28a, which is concentric with the crimp nut 28, is formed at the center of the lower surface of the crimp nut 28 so as to make contact with the external fixing portion 17 in a minute area. Has become.

The other structure is the same as that of the first embodiment.

FIG. 5B is a diagram showing the vibrating state of the ultrasonic motor of the second embodiment.

When a sinusoidal wave voltage 90 ° out of phase is applied to the ultrasonic motor of the second embodiment, the ultrasonic transducer 27
Since the protruding portion 28a in FIG. 2 is a fixed end, the bending vibration in the primary mode in which the fixed end serves as a node and the other end surface (upper end surface) of the ultrasonic transducer 27 becomes an antinode is It occurs as an elliptical vibration that rotates around the center. The rotor 18 pressed by the ultrasonic transducer 27 by this elliptical vibration
Rotates. In addition, the phase difference between the two sine wave voltages is 180
When it is shifted, the rotation direction of the elliptical vibration is reversed and the rotor 1
8 rotates in the opposite direction.

Also in the second embodiment, the resonator upper portion 23a has the circumferential groove 26 formed along the circumferential direction on the outer peripheral side surface as described above and the plurality of vertical grooves formed substantially parallel to the central axis. The groove 11 provides a displacement magnifying effect of converting the vibration obtained from the vibration generating section 24 into a large bending vibration. Further, by making the shape of the circumferential groove 26 trapezoidal, it is possible to obtain a vibration with a larger amplitude. Vibration generator 2
Since 4 has a shape substantially similar to the horn shape, the vibration force is concentrated on the narrowed portion of the outer shape, and the vibration is transmitted to the first resonator 23 corresponding to the above eight portions.

Further, the second resonator 15 and the external fixing portion 17
The vibration leaking to the external fixing portion 17 is suppressed in two steps by disposing an intermediate member such as the crimping nut 28, instead of directly contacting with. As for the vibration mode, as shown in FIG. 5B, the Y-direction vibration that was slightly left in the second resonator 15 can be completely reduced to 0 in the crimp nut 28 portion.

According to such a second embodiment, the first
Since a better supporting state can be obtained as compared with the examples,
The mechanical Qm has no damping due to the support, and can obtain high efficiency. A large amplitude is generated on the upper end surface of the ultrasonic transducer 27 due to the effect of the trapezoidal peripheral groove 26 in the first resonator 23, and high rotation and high torque are obtained.

Next, a third embodiment of the present invention will be described.

FIG. 7 is a sectional view (a) of an ultrasonic motor according to a third embodiment of the present invention, and (b) a diagram showing a vibrating state.

Since the basic structure of the third embodiment is similar to that of the first and second embodiments, only different points will be described.

The first resonator 30 arranged above the first and second piezoelectric elements 1 and 2 has basically the same shape as the first resonator 6 in the first embodiment. Having, bottom 3
It is a hollow cylindrical shape having 0b. The inside of the first resonator 30 above the bottom portion 30b is a cup-shaped hollow portion that forms an opening at the upper end surface, and vibrations at the upper end surface of the first resonator 30 occur. Are not regulated by the fastening member 9. Further, a plurality of vertical grooves 11 are formed on the outer peripheral side surface of the upper portion 30a of the first resonator 30 as in the first embodiment, and the resonator upper portion 30a is vibrated by dividing the upper portion 30a into eight vertical portions. Contributes to expansion. Further, in the circumferential direction of the outer peripheral side surface of the resonator upper portion 30a, a plurality of circumferential grooves 32 are formed toward the center.
Are formed.

On the other hand, below the second resonator 15 arranged below the first and second piezoelectric elements 1 and 2,
A crimp nut 33 is arranged as shown in the drawing, and the first and second piezoelectric elements 1 and 2 and the second resonator 15 are
It is configured to be sandwiched between the first resonator 30 and the crimp nut 33. As shown in the figure, the crimp nut 33
The lower surface of the has a conical shape, and its tip portion 33a comes into contact with the external fixing portion 17 with a very small area.

The other structure is the same as that of the first embodiment.

FIG. 7B is a diagram showing the vibrating state of the ultrasonic motor of the third embodiment.

When a sine wave voltage having a 90 ° phase shift is applied to the ultrasonic motor of the third embodiment, the tip portion 33a is applied.
Since it is a fixed end, a bending vibration of a primary mode in which the fixed end is a node and the upper end surface of the ultrasonic transducer is an antinode is generated as an elliptical vibration that rotates around the central axis.
This elliptical vibration causes the rotor 18 pressed by the ultrasonic vibrator to rotate. When the phase difference between the two sine wave voltages is shifted by 180 °, the rotation direction of the elliptical vibration is reversed and the rotor 18 rotates in the opposite direction.

Further, since the rigidity of the first resonator 30 is extremely lowered by the plurality of circumferential grooves 32, the difference in rigidity from the vibration generating portion is large. Therefore,
The vibration mode is Y in the vibration generator as shown in FIG. 7 (b).
It is possible to generate a vibration having a directional vibration of 0 and a maximum amplitude at the upper end surface of the first resonator 30.

Therefore, the position of the vibration node can be brought closer to the first resonator 30 side, and the vibration is completely suppressed at the crimping nut 33 portion, which serves as an ideal fixed end.
Further, since the vibration is minimized at the fixed end, the vibration is less likely to leak to the outside and the vibration loss due to friction is also eliminated.

The crimp nut 33 which is an intermediate member.
The tip portion 33a may have a substantially conical shape, or may have any shape as long as it is formed in the vicinity of the central axis and comes into contact with the external fixing portion 17 in a minute area.

According to the third embodiment, since the rigidity difference between the resonator and the vibration generating portion is made large, the node position of vibration approaches the first resonator 30 side, so that the crimp nut 33 supports it. The part to be turned becomes a node of complete vibration, and the vibration loss hardly occurs. Therefore, a highly efficient ultrasonic motor can be provided.

FIG. 8 is a side sectional view showing a modification of the ultrasonic motor of the third embodiment.

The first resonator 30 in the third embodiment described above.
Has formed a plurality of circumferential grooves 32 on the outer peripheral surface, this modified example has a plurality of circumferential grooves 3 formed on the inner peripheral surface of the first resonator 31.
They differ in that they form 2 '.

The other structure is the same as that of the third embodiment, and the operation and effect are also the same.

[0058]

As described above, according to the present invention, there is an effect that it is possible to provide a high-efficiency ultrasonic motor in which an ultrasonic vibrator is supported firmly and with almost no vibration loss.

[Brief description of drawings]

FIG. 1A is a side sectional view of an ultrasonic motor according to a first embodiment of the present invention, and FIG. 1B is a diagram showing a vibrating state.

FIG. 2 is an enlarged perspective view showing a polarized state of a piezoelectric element in the ultrasonic motor of the first embodiment.

FIG. 3 is an external perspective view showing an upper resonator in the first embodiment.

FIG. 4 is an enlarged sectional view of an essential part showing an enlarged contact portion between a lower resonator and a fixed portion in the first embodiment.

5A is a side sectional view of an ultrasonic motor according to a second embodiment of the present invention, and FIG. 5B is a diagram showing a vibrating state.

FIG. 6 is an enlarged sectional view of an essential part showing a contact portion between a crimp nut and a fixing portion in the second embodiment.

7A is a side sectional view of an ultrasonic motor according to a third embodiment of the present invention, and FIG. 7B is a diagram showing a vibrating state.

FIG. 8 is a side sectional view showing a modified example of the ultrasonic motor of the third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 1st piezoelectric element 2 ... 2nd piezoelectric element 3, 4, 5 ... Electrode plate 6 ... 1st resonator 8 ... Ultrasonic vibrator 9 ... Fastening member 10 ... Hollow part 11 ... Vertical groove 13 ... Vibration Generating part 14 ... Circumferential groove 15 ... Second resonator 15a ... Tip part 17 ... External fixed part 18 ... Rotor

Claims (2)

[Claims] 1. A first and a second electro-mechanical energy conversion element, which are positionally offset by 90 °, are rotated about a central axis by applying sinusoidal voltages whose phases are shifted by 90 ° to each other. An ultrasonic transducer that generates bending vibration, a driven member that is arranged on one of the end faces of the ultrasonic transducer, and a node position of the bending vibration that is generated on the ultrasonic transducer near the central axis. An ultrasonic motor comprising: a protrusion that is provided and is in contact with an external fixing member in a minute area. 2. A first and a second electro-mechanical energy conversion element, which are arranged with a positional shift of 90 °, are rotated about a central axis by applying sinusoidal voltages whose phases are shifted by 90 ° to each other. An ultrasonic transducer that generates bending vibration, a driven member that is arranged on one of the end faces of this ultrasonic transducer, and a vibration transmission that is provided at the node position of the bending vibration that occurs on the ultrasonic transducer. An ultrasonic motor comprising: a resonator formed of a low-speed material.