JPH0789746B2 - Surface wave motor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a stator composed of a piezoelectric element and an elastic body excited by the piezoelectric element, and an ultrasonic wave generated in the stator by pressure contact with the stator. The present invention relates to a surface wave motor including a moving element that is an elastic body that moves on the surface of the stator by a surface traveling wave of vibration.

“Prior Art” Surface acoustic wave motors that utilize ultrasonic vibration are devised in various ways to support and fix them so as not to interfere with the vibration of the stator that is the vibration source. There is something like this.

(1) A cushioning material such as felt is provided and supported on the surface opposite to the drive surface (the surface on which the rotor is pressed) of the stator.

(2) A plurality of auxiliary vibration members or flanges are provided and supported on the inner peripheral side or outer peripheral side of the stator on the neutral axis in the cross section of the stator.

[Problems to be Solved by the Invention] However, when the stator is supported by the method (1), the elastic coefficient (ordinary metal material) of the stator has an elastic coefficient about three times that of the piezoelectric element. Therefore, the neutral axis of flexure in the cross section of the stator is located approximately in the center in the thickness direction of the stator, and the vibration amplitude of the piezoelectric element and the vibration amplitude of the driving surface are almost equal. If a cushioning material such as felt is fixed to the surface (opposite to the surface) by adhesion or the like, the vibration of the piezoelectric element is hindered, and the amplitude of the drive surface is also reduced, which reduces the drive efficiency of the motor. there were. Further, the fact that the stator is pressed in the thickness direction between the felt or the like and the rotor also causes a decrease in the amplitude.

Further, when a plurality of auxiliary vibration members and flanges are provided and supported as in (2), the rigidity should be increased for the purpose of supporting, but if the rigidity is high, the energy loss due to the support increases. Therefore, when the auxiliary vibration member or the flange is provided so as to reduce the loss due to the support and to perform the support, the shape of the auxiliary vibration member is only thin and the width thereof is narrow, or the flange is extremely thin. Therefore, it is difficult and expensive to manufacture the auxiliary vibration member or the flange in order to reduce the loss due to the support.

Further, there is also a structure in which a large number of deep grooves are provided on the driving surface in order to increase the amplitude of the driving surface, but this structure also has the above-mentioned problem that the advantage of loss and the structural complexity and cost conflict with each other.

The present invention solves these problems and can reliably support the rotor or the stator, the loss due to the support is small, the amplitude of the driving surface can be increased, and the ultrasonic wave is excellent in cost. The object is to provide a surface wave motor that utilizes vibration.

“Means for Solving Problems” The gist of the present invention for achieving the above object is to provide a stator formed of a piezoelectric element and an elastic body excited by the piezoelectric element, and press-contacted to the stator. A surface wave motor comprising a moving body which is an elastic body that moves on the surface of the stator by a surface traveling wave of ultrasonic vibration generated in the stator, wherein at least one of the elastic bodies is made of a synthetic resin material. The one elastic body includes a vibrating portion having a surface against which the other elastic body is pressed, a supporting portion extending from the vibrating portion, and a held portion provided on the outer periphery of the supporting portion. The present invention resides in a surface wave motor characterized by being integrally molded.

"Operation" The vibrating part of the elastic body is supported by the support part integrally formed so as to extend in the circumferential direction from the vibrating part. The supported part is in the vicinity of the neutral axis of flexure during vibration, and the vibrating part is The rotor is rotated while vibrating ultrasonically while being reliably supported with the minimum loss.

Even with such a structure, since it is formed of a synthetic resin material, the vibrating portion, the supporting portion, and the held portion can be integrally molded and manufactured at low cost.

[Examples] Hereinafter, various examples of the present invention will be described with reference to the drawings.

1 is a perspective view of a stator of a surface acoustic wave motor according to a first embodiment of the present invention, and FIG. 2 is a sectional view of the stator of FIG. 1 and a rotor rotated by the stator. ing.

The stator 10 is composed of a piezoelectric element 15 and a ring-shaped elastic body 20 excited by the piezoelectric element 15, and the rotor 50 is composed of a ring-shaped elastic body 51 and a lining material 52.

The ring-shaped elastic body 20 includes a vibrating portion 25 excited by the piezoelectric element 15 and a supporting portion 30 extending on the outer periphery of the vibrating portion 25.
And a held portion 40 provided on the outer periphery of the support portion 30. The held portion 40 positions and holds the ring-shaped elastic body 20 with respect to the position where the surface acoustic wave motor is mounted. The ring-shaped elastic body 20 is integrally molded with a synthetic resin material such as engineering plastic, and preferably has a low elastic modulus suitable for operation.

The piezoelectric element 15 is bonded and fixed to the vibrating portion 25 of the ring-shaped elastic body 20 or is molded and fixed at the same time when the ring-shaped elastic body 20 is integrally molded. In the latter case, it becomes possible to omit the conventional bonding step.

As described above, it is desirable to have a low elastic modulus suitable for operation. Therefore, the elastic modulus of the ring-shaped elastic body 20 in this embodiment is about 1/10 of the elastic modulus of the piezoelectric element 15, and the density is 1 /. Five
In comparison, the elastic modulus of conventional metals is set to about 1/20, and the density is set to about 1/5.

When a metal or a material having a smaller elastic modulus and density than that of the piezoelectric element 15 is used, assuming that the shape of the stator 10 is the same as the conventional shape in terms of inner and outer diameters, the ring-shaped elastic body 20 Is about twice as thick. In addition, the neutral axis of bending vibration of the stator 10 was approximately the center (1/2) of the thickness of the stator 10 in the case of using a metal material in the past, but it is very close to the piezoelectric element 15. Can be located.

The support portion 30 is formed in a thin plate shape extending over the entire outer circumference of the vibrating portion 25 so that the condition for supporting the vibrating portion 25 is the same at any position in the circumferential direction of the vibrating portion 25. The outer peripheral surface of the portion 25 is connected to the vibrating portion 25 at a substantially central portion of the thickness thereof, that is, a neutral axis in bending of the vibrating portion 25 during vibration, and is not supported by the surface of the piezoelectric element 15.

The held portion 40 is formed into a frame shape on the outer periphery of the support portion 30, and is positioned and fitted into a fitting target, for example, a fitting groove formed in the lens barrel.

Next, the operation will be described.

When a voltage having a predetermined frequency is applied to the piezoelectric element 15, the vibrating section 25 and the piezoelectric element 15 integrally bend and vibrate, and the vibrating section 25
The mass point on the surface (driving surface) of the is displaced by the elliptical motion. The rotor 50 pressed against this surface rotates relative to the stator 10 by this elliptical motion, and a rotational force is obtained.

Since the support portion 30 is formed in a thin plate shape, the support portion 30 is easily displaced and connected to the vibrating portion 25 by the neutral shaft that is least affected, so that the vibrating portion 25 is not disturbed. . Since the vibrating portion 25 is supported on the entire circumference, the vibrating portion 25 is securely held, and uneven distribution of displacement does not occur.

In the present embodiment, since the ring-shaped elastic body 20 is made of a material having a low elastic modulus, the stator 10 is driven with respect to the same deflection amount (deformation amount) of the piezoelectric element 15 as compared with the case of using a metal material. The amount of deformation obtained on the surface is several times larger. When the amount of deformation increases, the elliptic motion of the surface mass of the driving surface also increases, and the output of the surface wave motor increases.

FIG. 3 shows a second embodiment, in which the supporting portion 30 is provided with a hole 31 for reducing the rigidity of the supporting portion.

Therefore, the support part 30 is symmetrical with the inner peripheral flange 32 connected to the entire circumference on the neutral axis of the vibration of the vibrating part 25, the rib part 33 formed between the hole part 31 and the hole part 31, and the inner peripheral flange 32. The outer peripheral flange 34 is connected to the held portion 40.

The inner peripheral flange 32 is provided all around the vibrating part
This is because when the vibrating portion 25 is supported, the constraint condition of the vibrating portion 25 does not change at any portion in the circumferential direction. Since the plurality of hole portions 31 are provided and the inner peripheral flange 32, the rib portion 33, and the outer peripheral flange 34 are formed in one plane, the rigidity of the support portion 30 against bending is reduced, and the vibrating portion 25 is less restrained. Can vibrate.

The rib portion 33 and the hole portion 31 have such dimensions that when the external load (rotational force) is applied to the rotor (not shown) and the load (rotational force) is applied to the stator 10, that is, the vibrating portion 25, the held portion 40 However, the vibrating unit 25 is set so as not to be displaced. The hole 31 may be formed as a thin portion that is thinner than other portions.

The held portion 40 is for fixing the stator 10 to a lens barrel, a motor housing, etc.
It suffices to set the shape of the held portion 40 by the fixing method described above, and the shape does not have to be the annular shape shown in the figure.

The stator of the surface wave motor has been described above, but the same can be explained for the rotor. In this case, the portion described as the piezoelectric element above serves as a lining material, and the held portion may be used to extract the rotational force of the rotor.
Further, depending on the configuration of the surface acoustic wave motor, the shape and position of the held portion may be changed to form the rotor.

In any case, the vibrating part, the supporting part, and the held part that make up the rotor can be made of synthetic resin material by integral molding,
The positional relationship between the vibrating part and the supporting part is the same as that of the stator.

[Advantage of the Invention] According to the surface acoustic wave motor of the present invention, since at least one of both elastic bodies is a synthetic resin material, the amplitude of ultrasonic vibration can be made larger even with the same input energy as when using a metal or the like. As a result, the efficiency of the surface acoustic wave motor can be improved.

In addition, since the vibrating portion, the supporting portion, and the held portion are integrally molded with the synthetic resin material, the vibrating portion, the supporting portion, and the held portion can be easily molded even if they have a complicated shape to achieve the purpose, and the cost can be reduced. it can.

Further, according to the embodiment, since the vibrating portion, the supporting portion, and the held portion are integrally formed of the low elastic material in the stator, even if the rigidity of the supporting portion is reduced (the driving efficiency is not reduced). As compared with the conventional metallic stator, the shape thereof is not thin and the supporting portion is not damaged when the surface wave motor is assembled.

Even when a hole is provided in the support to reduce the rigidity of the support, the vibrating part, the support, and the held part can be machined by integral molding. The advantage is that

[Brief description of drawings]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a perspective view of a stator, FIG. 2 is a cross sectional view of a stator and a rotor, and FIG. It is a top view of the stator concerning an example. 10 ...... Stator, 15 ...... Piezoelectric element 20 ...... Ring-shaped elastic body, 25 ...... Vibrating part 30 ...... Support part, 31 ...... Hole part 32 ...... Inner peripheral flange, 33 ...... Rib part 34 ...... Peripheral flange, 40 ... Held part 50 ... Rotor

Claims (2)

[Claims] 1. A stator composed of a piezoelectric element and an elastic body excited by the piezoelectric element, and a surface traveling wave of ultrasonic vibration generated in the stator, which is pressed against the stator, to move the surface of the stator. In a surface wave motor including a moving element that is a moving elastic body, at least one of the two elastic bodies is formed of a synthetic resin material, and the one elastic body has a surface against which the other elastic body is pressed. A surface acoustic wave motor comprising a vibrating portion, a support portion extending from the vibrating portion, and a held portion provided on the outer periphery of the support portion, which are integrally molded. 2. The surface wave motor according to claim 1, wherein the support portion is provided with a hole or a thin portion for adjusting the rigidity thereof.