JPH0475475A - Ultrasonic motor - Google Patents

Abstract

PURPOSE:To obtain an ultrasonic motor which does not generate unpleasant sound even if an overload, etc., is applied by forming a part of a rotor, receiving a pressure of a leaf spring in a thick disc, and providing a plurality of slender couplers between the disc and a part applied by a rotary motion from a stator. CONSTITUTION:A plurality of protrusions 20b of a rotor support 20 are radially extended from a thick disc 20a, with sufficiently smaller length and width than the wavelength of an aural sound. Thus, the protrusions 20b do not perform a role of a speaker, and do not almost generate unpleasant sound. Since the contact position of a rotor 23 in contact with a leaf spring 10 for pressurizing it is at a thick disc 20a at the center of the rotor, the vibration of the rotor 20 is merely slightly transmitted to the spring 10 side. Thus, radiation of the sound from the leaf spring can be reduced to prevent generation of unpleasant sound at this part. Thus, even if an overload, etc., is applied, generation of the unpleasant sound can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a traveling wave type ultrasonic motor, and more particularly to an ultrasonic motor that has been improved to prevent unpleasant noise from occurring when the motor is driven.

(Prior art) A traveling wave ultrasonic motor applies a high frequency voltage to a piezoelectric element to generate ultrasonic elliptical vibration on the stator surface, giving rotational motion to a rotor that is in pressurized contact. Compared to a motor, it has no windings and has a simple structure, and because it uses ultrasonic vibration energy, it is small and rotates at low speed.
It is attracting attention because of its advantages of high torque, high response, and excellent controllability due to friction force drive.

By the way, as a conventional traveling wave type ultrasonic motor, for example, one described in Japanese Patent Application Laid-Open No. 63-73887 is known.

This will now be explained with reference to FIG. 4. 1 is a case of the motor device body, and 2 is a cover.

A piezoelectric element 4 is fixed to the elastic body 3, and the elastic body 3 and the piezoelectric element 4 constitute a stator 5.

Further, a slider 7 is fixed to the ring 6 and constitutes a rotor 8.

This rotor 8 is pressed against the stator 5 by the pressing force of a disc spring 10 with a rubber body 9 in between, and rotates integrally with a shaft 11.

Note that the pressing force can be adjusted extremely easily since the thickness of the shim 12 is appropriately selected and adjusted and then held by the snap ring 13.

Further, the rubber body 9 has a vibration absorbing effect that prevents the elastic vibration generated in the rotor 8 from being transmitted to the shaft 11. Note that 14.15 is a bare link.

On the other hand, in this example, as can be seen from the illustrated cross-sectional shape, the rotor 8 is provided with a thin portion 8b adjacent to a thick flange portion 8a with which the stator 5 comes into pressure contact, and a disc spring 10 is provided on this thin portion 8b. is applied to the stator 5.
When the piezoelectric element 4 is excited by the resonance frequency of the rotor 8, the damping of the vibration of the rotor 8 is kept to a minimum.

(Problem to be Solved by the Invention) However, in the conventional ultrasonic motor as described above, since it is driven using vibration, the portion of the rotor where the disc spring makes pressure contact is thin, and the stator side The rotor is configured to efficiently propagate the vibrations generated by the rotor to the rotor. There was a problem where an unpleasant squealing sound was generated.

This is due to the fact that when an overload is applied, an excitation force is generated from the contact surface of the rotor and stator in the direction of the rotor due to frictional force fluctuations, which generates unnecessary vibrations in the audible range in the rotor. .

On the other hand, in order to prevent the unpleasant noises mentioned above from occurring, it is possible to increase the vibration damping rate by thickening the thin part of the rotor where the disc spring contacts with pressure, but this method does not reduce the necessary vibration. damped, resulting in a decrease in motor performance.

This invention was made in view of the above-mentioned conventional problems, and its purpose is to provide an ultrasonic motor that does not generate unpleasant noise even when overloaded or the like is applied. .

(Means for Solving the Problems) In order to achieve the above object, the present invention generates ultrasonic elliptical vibration on the stator surface by applying a high frequency voltage to a piezoelectric element, and applies pressure force between the stator and the disc spring. In an ultrasonic motor that provides rotational motion to a rotor that is brought into pressurized contact with the rotor, the portion of the rotor that receives the pressurizing force of the disc spring is a thick disk portion, and the rotor is rotated from the thick disk portion and the stator. It is characterized in that a plurality of thin connecting parts are provided between the part to which movement is applied.

(Function) In this invention, since the rotor is provided with a plurality of thin connecting parts between the thick disk part and the part to which rotational motion is applied from the stator, the part to which rotational movement is applied from the stator (
Almost no vibrations generated in the rotor body are transmitted to the coupling parts. As a result, the generation of unpleasant noise that has conventionally been emitted from the thin-walled portion of the rotor corresponding to the connecting portion is also significantly reduced.

In addition, since the portion of the rotor that receives the pressing force from the disk spring is a thick disk, the vibration components transmitted from this thick disk to the old spring are attenuated, and unpleasant noises are also prevented from occurring in this portion. reduced.

(Explanation of Examples) Hereinafter, this invention will be explained based on the drawings.

Note that this invention differs from the conventional example shown in FIG. 3 only in the rotor portion. Therefore, the following description will focus on the rotor portion, which is the gist of the present invention. Also, the same components as those used in the conventional example will be described with the same reference numerals.

FIG. 1 shows a first embodiment to which the present invention is applied, and FIG. 1(a) is a plan view of the rotor portion, and FIG.
is a sectional view taken along the line II in FIG.

In the same figure, reference numeral 20 denotes a rotor support part through which the shaft 11 is inserted, which includes a thick disc-shaped disc part 20a and a thin disc part 20a extending radially from the outer circumferential side of the thick disc part 20a. It is formed from nine protrusions (connecting parts) 20b. Note that the protrusion 20b has a length of 5 to 10 mm and a width of 1 to 10 mm.
The wavelength of audible sound is 20mnr-400mm.
(Frequency 20KH2 to IKH, Z) is sufficiently smaller in size.

Reference numeral 21 denotes a rotor body disposed in a ring shape at the lower part of the protrusion 20b via a vibration isolating rubber 22. There is pressure contact.

The rotor support section 20. The vibration isolating rubber 22 and the rotor body 21 constitute a rotor 23 according to this embodiment.

On the other hand, 24 is a rubber sheet disposed on the rotor support part 20, and is made of a rubber material having excellent low temperature characteristics such as silicone rubber.
It is pressed against the disc spring 10 with a rubber sheet 24 in between at the 0a portion.

Note that the vibration isolating rubber 22 disposed between the rotor support section 20 and the rotor main body 21 is also made of silicone rubber or the like so as not to transmit vibrations of the rotor main body 21 to the rotor support section 20 side.

The above is the configuration of the characteristic parts of the ultrasonic motor according to this embodiment, and its operation will be explained next.

First of all, the results of frequency analysis of the unpleasant squealing noise that occurs when the motor operates in the conventional example are shown in Figure 3 (a).
). As shown in the figure, it has five large vibration spectra. Figures (b) and (C) show frequencies of 7°581KH2 and 14.475KH2, respectively.
The vibration mode diagram is shown below. FIG. 3 is a diagram of the motor viewed from the rotor side.

The wavy lines are equal displacement lines. This results in the same figure (
In b), the out-of-plane deflection vibration is excited in the thick-walled flange portion 8a formed around the periphery of the rotor 8, and in the same figure (C), the vertical vibration in the thin-walled portion 8b receiving the pressing force of the disc spring 10 is excited. It can be seen that directional vibration (membrane vibration) is excited.

Similar vibration modes are excited in other parts of the vibration spectrum.

These vibrations use the surface of the thin portion 8b of the rotor 8 as a sound radiation surface to emit sound from the speaker. .

On the other hand, in this embodiment, as described above, the rotor 23 is connected to the rotor support section 20. The protruding portion 20b of the rotor support portion 20, which is composed of the vibration isolating rubber 22 and the rotor body 21 and is in contact with the rotor body 21 via the vibration isolating rubber 22, corresponds to the thin portion 8b in the conventional example.

By the way, the protrusions 20b are formed to project radially from the thick disc part 20a, and are only provided in a plurality (nine pieces), and have a length of 5 to 10 mm and a width of 1 to 4 mm, which corresponds to the wavelength of audible sound. It's small enough. Therefore, the protrusion 20b does not play the role of a speaker as in the conventional case, and only a small amount of sound is emitted.

Therefore, almost no unpleasant noise is generated.

Further, since the contact portion of the disc spring 10 that pressurizes the rotor 23 is the thick disk portion 20a which is the center portion of the rotor, the rotor 23
Only a small amount of vibration No. 3 is transmitted to the disk spring 10 side. Therefore, the radiation of sound from the disc spring portion can be significantly reduced, and the occurrence of unpleasant noises in this portion can be significantly prevented.

In addition, the rotor 23 is separated into the rotor support part 20 and the ring-shaped rotor body 21, and a vibration isolating rubber 22 made of silicone rubber or the like with excellent low-temperature properties is interposed between the two. The amount of vibration transmitted to the rotor support portion 20 side is attenuated, and generation of unpleasant noise is also prevented in this respect.

In this example, the same motor characteristics as the conventional example are obtained, with 1 oorpm at no load and a lock torque of 3 kgf*.
cm motor characteristics were obtained.

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

Figure (a) is a plan view of the rotor part, figure (b) is the figure (
It is a sectional view taken along the line ■-■ of a).

By the way, in this second embodiment, the rotor support part 20 and the rotor body 21 in the first embodiment are integrated to form the rotor 3.
3, and the anti-vibration rubber 22 is considered unnecessary.

That is, the rotor 33 is composed of a thick disk portion 31, a rotor main body portion 32, and nine connecting portions 34 formed radially between the two.

Therefore, the second embodiment has the advantage that the number of parts can be reduced and this type of ultrasonic motor can be obtained at low cost.

In addition, in this embodiment, the connecting portions 34 formed radially between the thick disk portion 31 and the rotor body portion 32 are configured to have the same thickness as the thick disk portion 31 and the rotor body portion 32. When the thickness of the connecting portion 34 is made thinner than that of the thick inner disk portion 31 and the rotor main body portion 32, the vibration generated in the rotor main body portion 32 becomes difficult to be transmitted to the thick inner disk portion 31 side, and the generation of unpleasant noise is further suppressed. It can be prevented.

(Effects of the Invention) As described above, in the ultrasonic motor according to the present invention, the portion receiving the pressing force of the disc spring constituting the rotor is a thick disk portion, and the thick disk portion and the stator are separated from each other. Since a plurality of thin connecting parts are provided between the parts subject to rotational motion, it is possible to largely prevent unpleasant noises from occurring even when an overload or the like is applied.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a rotor portion of a first embodiment to which the present invention is applied, FIG. 2 is an explanatory diagram of a rotor portion of a second embodiment to which the present invention is applied, and FIG. 3 is an explanatory diagram of a conventional example. FIG. 4 is a sectional view of the conventional ultrasonic motor. 3... Elastic body 4... Piezoelectric element 5... Stator 10... Belleville spring 11... Shaft 20... Rotor support portion 20a... Thick disk portion 20b... Projection (Connecting portion) 21... Rotor body 22... Vibration isolating rubber 23... Rotor 24... Rubber sheet 31... Thick disk portion 32... Rotor main body 33... Rotor 34 ... Connection patent applicant Nissan Motor Co., Ltd. Figure 1 Figure 4 Figure 2

Claims (1)

[Claims] 1. In an ultrasonic motor, an ultrasonic elliptical vibration is generated on the surface of a stator by applying a high frequency voltage to a piezoelectric element, and a rotor that is in pressure contact with the stator is rotated by a pressing force between the stator and a disc spring. A portion receiving the pressing force of the spring is a thick disk portion, and a plurality of thin connecting portions are provided between the thick disk portion and the portion to which rotational movement is applied from the stator. An ultrasonic motor featuring: