JP2018170952A - Vibration actuator and optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration actuator having high durability and quietness.SOLUTION: A vibration actuator 10 includes: an electromechanical transducer 11; an elastic body 12 which is vibrated by the electromechanical transducer 11; a moving member 15 that contacts the elastic body 12 and moves with respect to the elastic body 12; and a resin film 18 formed on a contact surface of at least one of the elastic body 12 and the moving member 15. In the resin film 18, a first filler having a density lower than that of polyamideimide serving as a base material of the resin film 18 is added.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a vibration actuator and an optical apparatus.

Conventionally, it has a vibrator in which an electromechanical conversion element and an elastic body are joined, and a progressive vibration wave (hereinafter referred to as a traveling wave) is generated in the elastic body using the expansion and contraction of the electromechanical conversion element. A vibration actuator that frictionally drives a relative movement member that is in pressure contact with a vibrator (elastic body) by a wave is known.
In this type of vibration actuator, the elastic body uses a highly elastic material such as a stainless steel metal material in order to efficiently transmit the applied vibration to the relative movement member.

  In such a vibration actuator, in response to demands for higher efficiency, improved driving stability, and improved durability, the material used for the frictional contact surface between the pressure contact vibrator and the relative movement member, or a combination of the materials Has been proposed.

  For example, Patent Document 1 proposes to arrange two layers of sliding materials having different functions on the contact surface of the relative movement member with the vibrator in order to reduce the durability and noise of the vibration actuator. First, for the first layer contacting the vibrator of the relative movement member, durability is improved by using a material having high wear resistance. Next, after the first layer, the second layer on the relative movement member side is provided with a sliding material for controlling the amount of strain and suppressing noise by pressurizing the vibration actuator (Patent Literature). 1).

JP-A-62-196079

  However, when a two-layer lining material is used on the contact surface of the relative movement member with respect to the vibrator, the first and second adhesive layers or adhesive interfaces exist, and the shear force is generated by the driving force generated by the vibration actuator. Insufficient strength may result, resulting in a decrease in generated torque, and the adhesive layer and adhesive interface may be destroyed.

  An object of the present invention is to provide a vibration actuator and an optical apparatus having high durability and quietness.

  The present invention solves the above problems by the following means.

The present invention includes an electromechanical conversion element, an elastic body that vibrates by the electromechanical conversion element, a moving member that contacts the elastic body and moves relative to the elastic body, and at least the elastic body and the moving member A resin film formed on one contact surface, and the resin film relates to a vibration actuator to which a first filler having a density lower than that of the polyamideimide serving as a base material of the resin film is added.
The present invention also relates to an optical apparatus provided with the vibration actuator.

  ADVANTAGE OF THE INVENTION According to this invention, the vibration actuator and optical apparatus provided with high durability and silence can be provided.

It is a figure which shows the camera of embodiment. It is a figure which shows the ultrasonic motor of embodiment. It is the figure which expanded the friction contact surface of the elastic body of the ultrasonic motor of embodiment, and a moving body. It is the figure which showed typically the structure in a resin film.

Hereinafter, an ultrasonic motor 10 having a vibrator 13 and a moving body 15 as a sliding body according to an embodiment of the present invention will be described. FIG. 1 is a diagram illustrating a camera 1 according to an embodiment including an ultrasonic motor 10.
The camera 1 includes a camera body 2 having an image sensor 6 and a lens barrel 3. The lens barrel 3 is an interchangeable lens that can be attached to and detached from the camera body 2. In addition, although the camera 1 of the present embodiment shows an example in which the lens barrel 3 is an interchangeable lens, the present invention is not limited thereto, and may be a lens barrel integrated with the camera body, for example.

The lens barrel 3 includes a lens 4, a cam barrel 5, an ultrasonic motor 10, and the like. In the present embodiment, an ultrasonic motor will be described as an example of a vibration actuator. The ultrasonic motor 10 has a substantially annular shape, and is disposed in the lens barrel 3 so that the center axis direction of the ring substantially coincides with the optical axis direction (the direction of arrow A in FIG. 1).
The ultrasonic motor 10 is used as a driving source for driving the lens 4 during the focusing operation of the camera 1. The driving force obtained from the ultrasonic motor 10 is transmitted to the cam cylinder 5. The lens frame 4a of the lens 4 is cam-engaged with the cam cylinder 5, and when the cam cylinder 5 rotates around the optical axis by the driving force of the ultrasonic motor 10, the lens 4 moves in the optical axis direction and is in focus. Adjustments are made.

  In FIG. 1, a subject image is formed on the imaging surface of the imaging device 6 by a lens group (including the lens 4) (not shown) provided in the lens barrel 3. The imaged subject image is converted into an electrical signal by the image sensor 6, and image data is obtained by A / D converting the signal.

FIG. 2 is a diagram showing an ultrasonic motor 10 having a vibrator 13 and a moving body 15 as a sliding body according to an embodiment of the present invention.
The ultrasonic motor 10 includes a vibrator 13 including a piezoelectric body 11 and an elastic body 12, a moving body 15, a flexible printed board 14, a vibration absorbing material 16, a support body 17 and the like.

  The piezoelectric body 11 has a function of converting electrical energy into mechanical energy. In this embodiment, a piezoelectric element is used as the piezoelectric body 11, but an electrostrictive element may be used. The piezoelectric body 11 is fixed to a support body 17 provided on the lens barrel 3 via a vibration absorbing material 16 such as felt.

The piezoelectric body 11 is electrically connected to the control device 101 via the flexible printed circuit board 14, and expands and contracts by a drive signal supplied from the control device 101 to excite the elastic body 12.
A temperature sensor 102 is connected to the control device 101, and a drive signal supplied to the piezoelectric body 11 is controlled so that the number of rotations of the ultrasonic motor 10 is constant according to the detection result of the temperature sensor 102. The frequency is adjusted.

The elastic body 12 is a member that generates a traveling wave when the piezoelectric body 11 is excited. The elastic body 12 is formed of an iron alloy such as stainless steel or invar steel having a high elastic modulus. The elastic body 12 of this embodiment is formed of SUS303.
The elastic body 12 is a substantially ring-shaped member. The piezoelectric body 11 is bonded to one surface by a conductive adhesive or the like, and the other surface is a comb formed by cutting a plurality of grooves 12b. The tooth part 12a is provided.
The front end surface of the comb tooth portion 12a is a contact surface that comes into pressure contact with the moving body 15 described later, and the moving body 15 is rotationally driven by a traveling wave generated on this surface.
A resin film 18 (see FIG. 3) having a polyamide imide resin as a main raw material and hollow glass beads in the vicinity of the surface is formed on the tip surface of the comb tooth portion 12a. Details of the method of forming the resin film 18 and the structure of the film will be described later.

The moving body 15 is a substantially ring-shaped member made of a metal such as aluminum. The moving body 15 of this embodiment is formed of an aluminum alloy.
The moving body 15 is brought into pressure contact with the vibrator 13 (elastic body 12) and is frictionally driven by a traveling wave. An alumite film layer 19 (see FIG. 3) is formed on the contact surface of the moving body 15 with respect to the vibrator 13.

  FIG. 3 is an enlarged view of a contact portion between the elastic body 12 and the moving body 15 as a sliding body of the ultrasonic motor 10. In FIG. 3, a part of the circumferential cross section of the ultrasonic motor 10 is enlarged.

  A resin film 18 is provided on a contact surface of the elastic body 12 with the moving body 15 (tip surface of the comb tooth portion 12a). An alumite film layer 19 is provided on the contact surface of the moving body 15 with the elastic body 12. Therefore, the surface in which the vibrator 13 and the moving body 15 are in frictional contact is in a form in which the resin film 18 and the alumite film layer 19 are in contact with each other.

(Paint composition ratio, painting process)
The resin film 18 is formed by the following coating process.
First, a degreasing process is performed on a contact surface of the elastic body 12 with the moving body 15 (tip surface of the comb tooth portion 12a). At this time, processing for roughening the surface such as blasting or etching may be performed to further improve the adhesion.

  Next, the solution used for forming the resin film 18 is a mixture of N-methylpyrrolidone mixed with 10 weight parts of hollow glass beads with respect to 100 weight parts of the polyamideimide resin. This solution is applied to the frictional contact surface of the elastic body 12, dried at 80 to 100 ° C. for 30 minutes to 1 hour, and then allowed to stand at a high temperature of about 230 to 280 ° C. for 15 to 30 minutes to dry and cure.

  After curing, the surface of the resin film 18 is polished and flattened by about 2 μm using green carborundum or the like. The surface roughness Rz (JIS B0601-2001) at that time is 0.5 μm or less, and the film thickness after polishing is 30 μm.

(Method for creating moving object 15)
On the other hand, the alumite film layer 19 is formed by subjecting the surface of the moving body 15 formed of an aluminum alloy (A6061) to anodization.

(Ultrasonic motor assembly)
The piezoelectric body 11 is joined to the elastic body 12 on which the resin film 18 is formed, and the vibrator 13 is formed. The vibrator 13 and the moving body 15 are arranged so that the resin film 18 of the vibrator 13 and the alumite film layer 19 of the moving body 15 are in contact with each other, and the respective members are assembled. Through these steps, the ultrasonic motor 10 is manufactured.

(Composition of resin film 18)
FIG. 4 is a cross-sectional view schematically showing the resin film 18 coated as described above.
The resin film 18 is a resin film whose main material is a polyamideimide resin 18a in which hollow glass beads 18b are blended.
The hollow glass beads 18b blended as the filler have a lower density than the polyamideimide resin 18a as the base material. For this reason, the amount of filler is increased in the vicinity of the surface of the resin film 18 due to the sintering after the film formation, and decreases from the vicinity of the surface to the lower layer. For example, the amount of filler is the largest near the surface and decreases step by step as it goes down. Here, the lower layer refers to the side closer to the elastic body 12 in the resin film 18.

That is, the contact surface of the vibrator 13 with the moving body 15 is composed of a single layer of sliding material (resin film 18) having two types of functions.
First, the outermost surface has a high amount of filler (hollow glass beads 18b) and high wear resistance. Furthermore, since the adhesive layer with the elastic body 12 has a small amount of filler, it maintains the adhesive strength, and at the same time absorbs vibrations that cause noise by lowering the viscosity and Young's modulus compared to the outermost surface with a large amount of filler Functions can be added.
That is, according to the present embodiment, high durability and quietness of the ultrasonic motor 10 can be realized simultaneously with a single layer of sliding material.
Note that a filler having a higher density than the resin material of the base material may be added to make the filler into two layers in the base material resin. In this case, noise is further alleviated by adding a filler that is higher in density than the resin material of the base material and that imparts vibration damping properties.

  Further, when the polyamideimide resin 18a is used as the main raw material of the resin film 18, the hardness, plastic deformation resistance, adhesion and peel strength, wear resistance, heat resistance are higher than when other resins are used as the coating film. In terms of properties, paint stability, processability, resistance to boiling water, etc.

In particular, in this embodiment, the polyamideimide resin 18a is used against the stress applied to the resin film 18 when the moving body 15 is in contact, so that the peel strength, wear resistance, and plastic deformation resistance of the resin film 18 can be improved.
Further, the adhesion to the resin film 18 and the vibrator 13 (elastic body 12) is improved, no primer is required, and the durability of the resin film 18 is improved. Furthermore, the heat resistance of the resin film 18 is improved, and the resin film 18 can be prevented from being deteriorated by frictional heat generated when the ultrasonic motor 10 is driven.

Further, the hollow glass beads 18 b that are present in the vicinity of the surface of the resin film 18 improve the wear resistance and heat resistance of the resin film 18 with respect to the moving body 15. Furthermore, the presence of the hollow glass beads 18b only in the vicinity of the surface does not lower the adhesive strength between the polyamideimide resin 18a, which is the main material of the resin film 18, and the elastic body 12.
As described above, the resin film 18 having this configuration contributes to improving the wear resistance, heat resistance, and durability of the ultrasonic motor 10.
Further, the resin film 18 contributes to improving the vibration damping performance of the ultrasonic motor 10. By using the resin film 18 of the present embodiment, the vibration absorbing material 16 can be omitted, and the cost can be reduced.

(Applicable to rod type motors)
In the above-described embodiment, the drive is taken out in the circumferential direction of the ring by the ring-shaped ultrasonic motor, but the shape having the output axis from the center of the ring in the direction perpendicular to the ring. The present invention may be applied to an ultrasonic motor (so-called rod-type ultrasonic motor). In particular, many rod-type ultrasonic motors are small in size, easily generate heat, and improvement in durability is desired. Therefore, by using the resin film 18 of this configuration, the wear resistance, heat resistance, and durability of the rod type motor can be improved.

<Deformation>
(About pigments)
In each embodiment, a pigment is not added, but a pigment such as carbon black or cobalt nickel may be blended.

(About anodized)
In each embodiment, although the example which uses hard anodized as anodized was shown, not only this but sulfuric acid anodized and oxalic acid anodized may be sufficient.

(Regarding the location of the resin film)
In each embodiment, although the example which forms the resin film 18 in the contact surface (comb tooth part 12a) of the vibrator | oscillator 13 was shown, not only this but a resin film may be formed in the contact surface of the mobile body 15. . Further, a resin film may be formed on both the contact surface of the vibrator 13 and the contact surface of the moving body 15.
Furthermore, the present invention may be applied to a vibration actuator in which the piezoelectric body and the moving body are in frictional contact without using an elastic body. In this case, a resin film may be formed on one of the contact surface of the piezoelectric body with respect to the moving body and the contact surface of the moving body with respect to the piezoelectric body.

(About elastic material)
In each embodiment, stainless steel is used as the material for forming the elastic body 12, but other iron-based materials may be used. For example, various steel materials such as S15C, S55C, SCr445, and SNCM630 may be used, or phosphor bronze and an aluminum alloy may be used.

(About mobile materials)
In each embodiment, although the moving body 15 showed the example formed with an aluminum alloy, not only this but iron-type material etc. may be used. For example, various steel materials such as S15C, S55C, SCr445, and SNCM630 may be used. Moreover, you may use resin with high heat resistance, such as a polyimide resin and PEEK (polyetherethertone) resin.

(Application to linear drive actuator)
In each embodiment, the ultrasonic motor in which the moving body 15 is driven to rotate is shown.

(Applicable to vibration actuators that do not use the ultrasonic range)
In the embodiment, the ultrasonic motor using the vibration in the ultrasonic region has been described as an example. However, the present invention is not limited thereto, and the present invention may be applied to, for example, a vibration actuator that uses vibrations outside the ultrasonic region.

(Applied to other than cameras)
In each embodiment, the example in which the ultrasonic motor 10 is used as a drive source that performs the focusing operation of the lens barrel of the camera has been described. It may be used. Further, the ultrasonic motor 10 may be used for a driving source such as a copying machine, a steering wheel tilt device of an automobile, a driving unit of a headrest, or the like.

  1: camera, 2: camera body, 3: lens barrel, 10: ultrasonic motor, 11: piezoelectric body, 12: elastic body, 13: vibrator, 15: moving body, 18: resin film, 18a: polyamideimide Resin, 18b: Hollow glass beads, 19: Anodized coating layer

Claims (6)

An electromechanical transducer,
An elastic body that vibrates by the electromechanical transducer;
A moving member that contacts the elastic body and moves relative to the elastic body;
A resin film formed on at least one contact surface of the elastic body and the moving member,
The resin film is a vibration actuator in which a first filler having a density lower than that of polyamideimide as a base material of the resin film is added. The vibration actuator according to claim 1,
The resin film is a vibration actuator formed by firing. The vibration actuator according to claim 1 or 2,
The first filler is a vibration actuator that is a hollow glass bead. The vibration actuator according to any one of claims 1 to 3,
The resin film includes a second filler having a higher density than the polyamideimide,
The second filler is a vibration actuator that has a lot in the vicinity of a contact surface with the elastic body or the moving member opposite to the surface of the resin film, and decreases as the distance from the contact surface increases. The vibration actuator according to any one of claims 1 to 4,
The resin film is a vibration actuator including N-methylpyrrolidone.   An optical apparatus comprising the vibration actuator according to claim 5.

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