JPH06121554A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To provide an ultrasonic motor which can rotate stably at high efficiency even upon application of radial load to an output transmission shaft. CONSTITUTION:An elastic member 29 is placed between a mover 27 and an output transmission shaft 28 for transmitting rotation of the mover 27 to an external load. An output take-out part 28b of the output transmission shaft 28 is provided on the side of a bearing 31 located on the oscillator 24 side in order to regulate the rotational position of the output transmission shaft 28 thus taking out output from the oscillator 24 side of the output transmission shaft 28. Since the distance between a fulcrum, i.e., the bearing 31, and a working point is short, deformation of the output transmission shaft 28 due to load functioning thereon can be retarded when abnormal force is applied radially to the output transmission shaft 28. Furthermore, deformation absorbing effect of the elastic member 29 mounted on the mover 27 can be exhibited by providing the output transmission shaft 28 with a free end at a part coming into contact with the elastic member 29.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor which uses elastic vibration excited by a piezoelectric body as a driving force, and more particularly to an output transmission mechanism of the ultrasonic motor.

[0002]

2. Description of the Related Art In recent years, attention has been paid to an ultrasonic motor which drives a vibrating body composed of a piezoelectric body such as a piezoelectric ceramic and an elastic substrate such as a metal with an AC voltage to excite elastic vibration, and which uses the driving force as a driving force. ing. Hereinafter, a conventional ultrasonic motor will be described with reference to the drawings.

FIG. 2 is a vertical sectional view of a conventional ultrasonic motor. In FIG. 2, a vibrating body 3 is formed by laminating a piezoelectric body 2 on one surface of the elastic substrate 1.
A plurality of protrusions 1a are provided on the other surface of the. Reference numeral 4 is an elastic body, and 5 is a friction material made of a wear resistant material, which are bonded to each other to form a moving body 6. 7
Is an output transmission shaft that transmits the rotation of the moving body 6 to the outside,
At the end of the output transmission shaft 7 on the side of the moving body 6, there is provided a protrusion 7a for transmitting the rotation of the moving body 6 stably and efficiently, and the output extraction further protruding outward from the protrusion 7a. The rotation is taken out from the portion 7b. Reference numeral 8 denotes an elastic member having a large friction coefficient, which is interposed between the protrusion 7a of the output transmission shaft 7 and the moving body 6 and absorbs and corrects abnormal vibration of the output transmission shaft 7 to stabilize the rotation of the moving body 6. The power is efficiently transmitted to the output transmission shaft 7. Reference numeral 9 denotes a supporting member that supports the vibrating body 3 without inhibiting the vibration of the vibrating body 3, and 10 denotes a bearing,
Reference numeral 11 is a disc spring. Reference numeral 12 is a pressing force adjusting means for adjusting the pressing force of the disc spring 11, and the pressure-controlled disc spring 11 is used.
Thus, the moving body 6 is brought into pressure contact with the vibrating body 3 via the friction material 5. Reference numeral 13 is a base portion that supports the ultrasonic motor, and the vibrating body 3 is installed on the base portion 13 via the support member 9, and the bearing 10 is also installed on the base portion 13, so that the output transmission shaft 7 The position is regulated.

In the ultrasonic motor configured as described above, when an alternating electric field is applied to the piezoelectric body 2, a bending vibration that advances in the circumferential direction is excited in the vibrating body 3, and the friction material 5 and the protruding body of the vibrating body 3 are excited. The moving body 6 is caused by the frictional force acting between 1a.
Is driven in the direction opposite to the traveling direction of the traveling wave.

FIG. 3 shows the piezoelectric body 2 in the ultrasonic motor.
FIG. 3 is a plan view showing an example of the electrode structure of FIG. 1, which is configured to excite four-wave bending vibration in the circumferential direction. In FIG.
A0 and B0 are drive electrodes each including a small region corresponding to a half wavelength of the traveling wave excited. C0 is an electrode having a length corresponding to a quarter wavelength, and D0 is an electrode having a length corresponding to a quarter wavelength, and is provided to make a positional shift corresponding to a quarter wavelength on the drive electrodes A0 and B0. Has been. Therefore, the drive electrode of A0 and the drive electrode of B0 have a phase difference of a quarter wavelength (= 90 degrees) with each other. Also,
Adjacent one-half wavelength equivalent small electrode portions in the drive electrodes A0 and B0 are alternately polarized in opposite directions in the thickness direction. The bonding surface of the piezoelectric body 2 with the elastic substrate 1 is the surface opposite to the surface shown in FIG. 3, and the electrode is a full-surface electrode. When used, as indicated by hatching, the small regions forming the drive electrode A0 and the drive electrode B0 are short-circuited and used.

The drive electrodes A0 and B0 have the formula (1),
When the voltages V1 and V2 represented by the equation (2) are respectively applied, the traveling wave of bending vibration traveling in the circumferential direction represented by the equation (3) is excited in the vibrating body 3.

V1 = V0sin (ωt) (1) V2 = V0cos (ωt) (2) ξ = ξ0cos (ωt−kx) (3) where V0 is the maximum voltage value, ω is the angular frequency, t is the time, ξ is the bending vibration amplitude value, ξ0 is the maximum bending vibration amplitude value, k is the wave number, and x is the position.

FIG. 4 is an explanatory view for explaining the operation principle.
In FIG. 4, when a traveling wave is excited in the vibrating body, the point A on the surface of the vibrating body 3 makes an elliptic motion of the long axis w and the single axis u, and the moving body placed under pressure on the vibrating body 3 is installed. 6 is in contact with the vicinity of the apex A of the ellipse drawn by an arbitrary point on the surface of the vibrating body 3 through the friction material 5, and due to the frictional force, the velocity expressed by the equation (4) in the direction opposite to the traveling direction of the wave. It shows a state of exercising with v.

V = ω × u (4) FIG. 5 is an equivalent circuit seen from the drive terminal of the vibrating body, which has an electric capacity Cel4, an electric system-mechanical system conversion transformer (conversion coefficient N) 15, and a mechanical elastic constant Cml6. , Mass Lml7,
It is expressed as mechanical loss Rml8 and is output as force F. When the voltage V is applied to the piezoelectric body, the total current il9 flows. The total current il9 is composed of an electric arm current ie20 which is a current flowing through the electric capacity Cel4 and a mechanical arm current im21 which is a current flowing through the electric system-mechanical system conversion transformer 15. This mechanical arm current im21 is the displacement speed vd represented by the equation (5) by the electric system-mechanical system conversion transformer 15.
Is converted to.

Vd = dξ / dt (5) Therefore, the total current il9 or the mechanical arm current im21
The displacement ξ can be obtained by

From these facts, the rotation speed of the moving body is proportional to the instantaneous value of the bending vibration amplitude of the vibrating body, and the instantaneous value of the bending vibration amplitude corresponds to the mechanical arm current im flowing in the piezoelectric body forming the vibrating body. Proportional. Therefore, the rotation speed of the moving body can be stably controlled by detecting the mechanical arm current im and using it.

[0012]

However, in the ultrasonic motor having the structure shown in FIG. 2, the output take-out portion 7b of the output transmission shaft 7 is used.
When a radial load is applied to the bearing, this load is applied to the bearing 1.
Since 0 acts as a fulcrum, the distance between the fulcrum and the acting point becomes large, the output transmission shaft 7 is largely deflected even with a small load, and the protrusion 7a of the output transmission shaft 7 and the elastic member 8 or the elastic member 8 and the moving body 4 are separated. The contact state changes and becomes unstable, and the contact state between the friction material 5 of the moving body 6 and the protrusion 1a of the vibrating body 3 also changes. Since the ultrasonic motor takes out the output by utilizing the friction between the moving body 6 and the vibrating body 3, when the contact state between the two changes, the transmission efficiency of the rotation from the moving body 6 to the output transmission shaft 7, and There is a problem that the efficiency of transmission of rotation from the vibrating body 3 to the moving body 6 is reduced, and it becomes impossible to take out the output to the outside stably and efficiently.

The present invention solves the above problems, and an object of the present invention is to provide an ultrasonic motor which can be stably and efficiently driven even when a radial load is applied to the output transmission shaft. is there.

[0014]

In order to solve the above-mentioned problems, the ultrasonic motor of the present invention has a moving body which is affected by a load acting on the output transmission shaft, particularly when a radial force acts on the output shaft. And the contact part of the vibrating body, the elastic member and the output transmission shaft, and the contact state of the elastic member and the moving body do not show a large change. Therefore, for example, when the bearing is installed on the vibrating body side as in the ultrasonic motor taken as the conventional example, the output is taken out from the vibrating body side of the output transmission shaft.

[0015]

With the above structure, the output take-out portion is provided on the side where the bearing for positioning the output transmission shaft is provided, and the mechanical output is taken out from the side where the bearing is installed, that is, the vibrating body side or the moving body side of the output transmission shaft. , Even if an abnormal radial force is exerted on the output transmission shaft, the distance between the fulcrum bearing and the action point is short, so the deformation of the output transmission shaft due to the load acting on the output transmission shaft can be reduced, and as a result,
The influence on the contact situation between the moving body and the vibrating body can be reduced. Also, the contact portion of the output transmission shaft with the elastic member is a free end,
By making the displacement absorbing effect of the elastic member provided on the moving body effective, the moving body is affected by the poor machining accuracy of the shaft and the deformation and displacement of the output transmission shaft due to the load acting on the output transmission shaft. The ultrasonic motor can be stably and efficiently driven without being transmitted to the contact surface of the vibrating body.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view of an ultrasonic motor according to an embodiment of the present invention. In FIG. 1, a vibrating body 24 is configured by laminating a piezoelectric body 23 on one surface of the elastic substrate 22, and a plurality of protrusions 22 a are installed on the other surface of the elastic substrate 22. Reference numeral 25 is an elastic body, and 26 is a friction material made of a wear-resistant material, which are bonded together to form a moving body 27. Reference numeral 28 denotes an output transmission shaft that transmits the rotation of the moving body 27 to the outside.
Is provided with a protrusion 28a for efficiently transmitting rotation from the moving body 27, and an output extended toward the vibrating body 24 side opposite to the moving body 27. The rotation is taken out from the take-out portion 28b. Reference numeral 29 is an elastic member interposed between the protrusion 28a of the output transmission shaft 28 and the moving body 27, and absorbs and corrects the waviness of the contact surface between the vibrating body 24 and the moving body 27, the shake of the output transmission shaft 28, and the like.

Reference numeral 30 is a support member for supporting the vibrating body 24 without disturbing the vibration of the vibrating body 24. Reference numeral 31 denotes a bearing A provided on the vibrating body 24 side, and the output transmission shaft 2
8 position regulation is performed. Reference numeral 32 is a disc spring, and 33 is a pressurizing force adjusting means for adjusting the pressurizing force of the disc spring 32.
It is in pressure contact with the vibrating body 24 via. Reference numeral 34 is a bearing B that supports the other end of the output extracting portion 28b of the output transmission shaft 28. Reference numeral 35 denotes a base portion that supports the ultrasonic motor. The vibrating body 24 is installed on the base portion 35 via the support member 30, and the bearings 31 and 34 are also installed on the base portion 35.

The operation of the ultrasonic motor thus constructed will be described below. When an alternating electric field is applied to the piezoelectric body 23, a traveling wave of bending vibration is excited in the vibrating body 24 in the circumferential direction, and the moving body 27 is moved by the frictional force acting between the friction material 26 of the moving body 27 and the protrusion 22a. Is driven and rotated in the direction opposite to the traveling direction of the traveling wave. This rotation is caused by the elastic member 2
It is transmitted to the output transmission shaft 28 via 9. Here, the rotation of the ultrasonic motor with respect to the outside is taken out from the output take-out portion 28b of the output transmission shaft 28 on the side opposite to the moving body 27 with respect to the vibrating body 24, so that the output transmission shaft 28 is radially moved. Even if an abnormal force is applied to the output transmission shaft 28, since the distance between the fulcrum bearing A31 and the point of action is short.
Deformation of the moving body 27 and the vibrating body 2 can be reduced.
It is possible to reduce the influence of No. 4 on the contact situation.

The output take-out portion 28 of the output transmission shaft 28
Even if a radial load is applied to b, the protrusion 28a of the output transmission shaft 28 is a free end and can be freely displaced without being constrained, so that the elastic member 29 can be securely moved.
It can be sandwiched between the protrusions 28a of the output transmission shaft 28, and due to the correction effect of the elastic member 29, the effect of radial load is unlikely to appear on the contact surface between the vibrating body 24 and the moving body 27. As a result, even if a radial load is applied to the output take-out portion 28b, the vibrating body 24 moves to the moving body 27 and the moving body 2 moves.
The rotation is transmitted from 7 to the output transmission shaft 28 stably and efficiently, and the ultrasonic motor can be stably and efficiently driven.

The present invention is not limited to the above embodiment, but various modifications can be made based on the gist of the present invention. For example, when the bearing is installed on the side of the moving body, it goes without saying that if the output is taken out from the side of the moving body, the same effect as the above-described embodiment can be obtained.

[0021]

As described above, according to the ultrasonic motor of the present invention, even when a radial load is applied to the output transmission shaft, the bending of the shaft due to the radial load can be reduced, and the moving body and the vibrating body can be reduced. It is possible to reduce the influence on the contact surface and the power transmission between the moving body and the output transmission shaft, and it is possible to provide an ultrasonic motor with stable operation and high driving efficiency.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an ultrasonic motor according to an embodiment of the present invention.

FIG. 2 is a vertical sectional view of a conventional ultrasonic motor.

FIG. 3 is a plan view showing an electrode structure of a piezoelectric body in an ultrasonic motor.

FIG. 4 is an explanatory diagram of the operation principle of the ultrasonic motor.

FIG. 5 is an equivalent circuit diagram of a piezoelectric body in an ultrasonic motor.

[Explanation of symbols]

 24 vibrating body 27 moving body 28 output transmission shaft 28b output extracting section 29 elastic member 31, 34 bearing 35 base section

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Masanori Sumihara 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Takahiro Nishikura, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Osamu Kawasaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] 1. A piezoelectric body is driven by an AC voltage, and an elastic traveling wave is excited in a vibrating body composed of the piezoelectric body and an elastic body, so that the vibrating body is placed in pressure contact with the vibrating body. An ultrasonic motor for rotating a moving body, wherein an elastic member is interposed between the moving body and an output transmitting shaft for transmitting the rotation of the moving body to an external load, and the output transmitting shaft is provided on the vibrating body side or the moving body side. The ultrasonic motor is characterized in that a bearing for restricting the rotational position of the output transmission shaft is installed and an external output is taken out from the vibrating body side or the moving body side of the output transmission shaft.