JP2537947C - - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor using ultrasonic vibration by a piezoelectric body. 2. Description of the Related Art In general, an ultrasonic motor has a configuration in which a moving body and a vibrating body made of a metal elastic body having a piezoelectric element having electrodes fixed thereto are brought into pressure contact with each other. The principle is that a traveling wave of ultrasonic vibration is generated in the element and the vibrating body as shown in FIG. 5, and the moving body is driven by the frictional force between the vibrating body and the moving body to obtain mechanical energy. In FIG. 5, reference numeral 1 denotes a piezoelectric element, and a metal elastic body 2 is adhered and fixed to the surface of the piezoelectric element to form a vibrating body. Reference numeral 3 denotes a moving body, on which a friction material 4 is fixed. When an electric input is applied to the piezoelectric element 1, a traveling wave of ultrasonic vibration in the direction A is generated in the metal elastic body 2. Each mass point of the metal elastic body 2 has an elliptical motion like B, and each wave front has a property of moving laterally in a direction opposite to the traveling wave direction. The valley portion of the traveling wave has the property of moving sideways in the same direction as the traveling wave. Therefore, the moving body 3 placed on the surface of the metal elastic body 2 contacts only the upper part of the crest and is driven laterally in the direction C by the frictional force with the metal elastic body 2. In such an ultrasonic motor, iron, stainless steel, aluminum, or the like is used as the material of the metal elastic body 2 and the moving body 3. The piezoelectric element 1 is provided on both surfaces of a plate-like piezoelectric ceramic separated in a predetermined direction.
In order to excite the traveling wave, a plurality of divided electrodes having a predetermined shape are attached and formed. One surface of the plate-like piezoelectric element on which the electrodes are formed is adhered and fixed to the metal elastic body 2 using an adhesive to form a vibrating body. Problems to be Solved by the Invention When an ultrasonic motor having the above configuration is driven in a high-humidity atmosphere, the electrodes formed on the surface of the piezoelectric ceramic cause electrical insulation failure and the motor stops driving. is there. Further, there is a problem that the adhesion between the piezoelectric element and the metal elastic body is peeled off or the piezoelectric ceramic is cracked due to the deterioration of the adhesive force due to the moisture absorption of the adhesive portion. The present invention has been made in view of the above problems, and an object of the present invention is to provide an ultrasonic motor which does not cause electrical insulation failure and has excellent humidity resistance reliability in a high humidity atmosphere. It is another object of the present invention to provide an ultrasonic motor having excellent humidity resistance without peeling or cracking of a piezoelectric element in a high humidity atmosphere. Means for Solving the Problems In order to achieve the above object, the present invention comprises a plate-like piezoelectric element to which electrodes are attached, which is covered with a flexible moisture-resistant resin. Another means is to coat the surface of the adhesive exposed on the bonding surface between the piezoelectric element and the metal elastic with a flexible moisture-resistant resin. In another means, the surface of the plate-shaped piezoelectric element to which the electrodes are attached and the surface of the adhesive portion between the piezoelectric element and the metal elastic body are covered with a flexible moisture-resistant resin. Still another means is that the surface of the plate-like piezoelectric element to which the electrode is attached or (and)
The surface of the adhesive part between the piezoelectric element and the metal elastic body is covered with a flexible resin, and further covered with a moisture-resistant resin. According to the above configuration, the surface of the plate-shaped piezoelectric element to which the electrodes are attached is covered with a flexible moisture-resistant resin, so that the invasion of moisture between the electrode portions and the electrodes is suppressed. The electrical insulation of the electrode portion is improved, and since the coating resin has flexibility, it can be easily deformed in accordance with the vibration of the piezoelectric element, so that the influence on the resonance frequency is small, and Thus, it is possible to obtain an ultrasonic motor having excellent moisture resistance reliability such as no cracking or peeling of the coating resin. In addition, since the surface of the adhesive between the piezoelectric element and the metal elastic body is covered with a flexible moisture-resistant resin, penetration of moisture into the adhesive portion is suppressed. And the coating resin has flexibility, so that it can be easily deformed according to the vibration of the piezoelectric element and the metal elastic body, so that the influence on the resonance frequency is small. It is possible to obtain an ultrasonic motor having excellent moisture resistance reliability such as no cracks or peeling. In addition, the surface of the plate-like piezoelectric element to which the electrodes are attached and the surface of the adhesive part between the piezoelectric element and the metal elastic body are covered with a flexible moisture-resistant resin, so that the electrode part and the adhesive part are covered. Since the intrusion of moisture is suppressed, the electrical insulation of the electrode part is improved, and the deterioration of the adhesive force of the adhesive part and the cracking of the piezoelectric ceramic are reduced, and at the same time, the coating resin has flexibility. Since it can be easily deformed in response to the vibration of the piezoelectric element and metal elastic body, it has little effect on the resonance frequency, and has excellent moisture resistance reliability such as no cracking or peeling of the coating resin An ultrasonic motor can be obtained. Further, the surface of the plate-like piezoelectric element to which the electrodes are attached and / or the surface of the adhesive part between the piezoelectric element and the metal elastic body are covered with a flexible resin, and furthermore, a moisture-resistant resin is further applied thereon. By coating, the penetration of moisture into the electrode portion and the adhesive portion is suppressed, so that the electrode-like insulation of the electrode portion is improved, and the adhesive force of the adhesive portion is not deteriorated and the piezoelectric body is less cracked. At the same time, since the flexible resin is formed in the inner layer, the vibration generated in the piezoelectric element and the metal elastic body is mechanically absorbed, the influence on the resonance frequency is small, and the flexible resin and the moisture resistant It is possible to obtain an ultrasonic motor having excellent moisture resistance reliability such as no cracking or peeling of the conductive resin. Example (Example 1) An example of a main configuration of an ultrasonic motor having excellent moisture resistance reliability according to the present invention, that is, a piezoelectric ceramic, an electrode, a metal elastic body, a moving body, and a flexible moisture resistant resin coating part. FIG. 1 shows an example of each laminated structure and arrangement relationship. As shown in the drawing, a plurality of divided electrodes 12 are formed on both surfaces of a piezoelectric ceramic 11 polarized in a predetermined direction. One surface of the plate-shaped piezoelectric element 1 on which the electrodes are formed is bonded and fixed to the metal elastic body 2 using an adhesive 5. 6
Is a flexible moisture-resistant resin layer, of which 61 is a flexible moisture-resistant resin layer covering the surface of the plate-shaped piezoelectric element 1 on which electrodes are attached, and 2 is a piezoelectric moisture-resistant resin layer. The flexible moisture-resistant resin layer is coated on the exposed surface of the adhesive 5 at the joint with the metal elastic body 2. The vibrating part 7 is constituted by the metal elastic body 2 to which the piezoelectric element 1 is adhered and the flexible moisture-resistant resin 6. The moving unit 8 has a structure in which a friction member 4 is fixed to a moving body 3 as a main body and an operation surface, and the friction material 4 and the surface of the metal elastic body 2 are in pressure contact. The flexible moisture-resistant resin is not particularly limited, but a flexible moisture-resistant resin such as a silicone resin, a fluorine resin, a synthetic rubber, a urethane resin, and a flexible polyester resin can be used. Hereinafter, the present invention will be described in more detail with reference to specific examples. As shown in FIG. 2 (a), a disk-type ultrasonic motor having a diameter of 40 mm and a thickness of 8 mm was used. In FIG. 2a, the vibrating portion 7 of the ultrasonic motor has substantially the same diameter on the surface of a 0.5 mm-thick disk-shaped piezoelectric ceramic 11 on which a silver 5 μm-thick electrode 12 is attached. The back surface of the stainless steel elastic body 2 having a circumferential arrangement of a large number of projection segments 21 on the front surface is bonded and fixed using an adhesive 5 made of epoxy resin, and the disk-shaped piezoelectric ceramic 11 on which the electrodes 12 are attached is formed. The other surface and the exposed surface of the adhesive layer 5 are coated with silicone resin paint to a thickness of 0.5 mm, applied and dried to form flexible moisture-resistant resin layers 61 and 62, respectively. It is. The protruding segment 21 is provided for facilitating mechanical vibration of the vibrating portion 7 and increasing vibration. Disk-shaped stainless steel moving body 3 constituting corresponding moving section 8
A friction material 4 made of a composite plastic is adhered and fixed. Although not shown, the vibrating portion 7 and the moving portion 8 are pressed against each other by an appropriate spring tightening means, and the surface of the protrusion 21 of the elastic body 2 and the friction material 4 are in contact with each other. The external view of the piezoelectric element 1 is shown in FIG.
As shown in FIG. 2B, an electrode 12 obtained by applying and baking a silver paint is formed on the surface of a disk-shaped piezoelectric ceramic 11 having a thickness of about 0.5 mm. In such an electrode arrangement, the electrodes are divided into two sets and connected, and the phase is changed by 90 degrees with respect to time to about 70 KHz.
By inputting a power of 80V with a resonance frequency of
The traveling wave of the wave is excited. The output performance of the ultrasonic motor thus obtained at 24 ° C. and 60% RH was a no-load rotation speed of 500 rpm and a starting torque of 1200 gf-cm. 40 ℃
When the apparatus was driven in a high-humidity atmosphere of 90% RH for 200 hours under no load, no abnormalities such as leakage of the electrode portion, stopping of the motor, peeling or cracking of the piezoelectric body were observed. In addition, no crack was generated in the flexible moisture-resistant resin. Further, the output characteristics after that are 24
At 0 ° C., the no-load rotation speed was 500 rpm and the starting torque was 1200 gf-cm, which were the same as the initial values. On the other hand, in the above ultrasonic motor configuration, the ultrasonic motor in which the surface of the piezoelectric element on which the electrodes are formed is not coated with the silicone resin is driven in a high humidity atmosphere of 40 ° C. and 90% RH. Then, the electrode portion leaked and the ultrasonic motor stopped driving. In addition, the ultrasonic motor which does not cover the surface of the adhesive portion with the silicone resin has a temperature of 40 ° C.
When driven in a high humidity atmosphere of 90% RH, the adhesion between the piezoelectric element and the metal elastic body was peeled off after about 100 hours, the piezoelectric ceramic was cracked, and the ultrasonic motor stopped operating. As is clear from the above Examples and Comparative Examples, the surface of the disk-shaped piezoelectric ceramic on which the electrodes are attached and / or the surface of the adhesive layer between the piezoelectric element and the metal elastic body are provided with a flexible moisture-resistant material. By coating with a conductive resin, it is possible to obtain an ultrasonic motor having excellent moisture resistance reliability such that there is no insulation failure between electrodes in a high-humidity atmosphere, and no deterioration in adhesive strength or breakage of piezoelectric ceramics occurs. it can. Second Embodiment FIG. 3 shows another example of the configuration of the main part of the ultrasonic motor having excellent moisture resistance reliability according to the present invention. A plurality of divided electrodes 12 are attached to both surfaces of a piezoelectric ceramic 11 polarized in a predetermined direction. One surface of the plate-shaped piezoelectric element 1 on which the electrodes are formed is bonded and fixed to the metal elastic body 2 using an adhesive 5. Reference numeral 6 denotes a flexible moisture-resistant resin layer composed of two layers, which is a feature of the present invention. Among them, 61a denotes a flexible resin coated on the surface of the plate-shaped piezoelectric element 1 on which electrodes are formed. Layers,
The upper surface is covered with a moisture resistant resin 61b. A flexible resin layer 62a is coated on the exposed surface of the adhesive 5 between the piezoelectric element 1 and the metal elastic body 2, and has a structure in which a moisture-resistant resin layer 62b is coated on the upper surface. The vibrating part 7 is constituted by the metal elastic body 2 to which the piezoelectric element 1 is adhered and the flexible moisture-resistant resin 6. The moving unit 8 has a configuration in which the friction material 4 is fixed to the operating surface of the moving body 3 as a main body, and the friction material 4 and the surface of the metal elastic body 2 are in pressure contact. The flexible resins 61a and 62a are not particularly limited, but flexible resins such as synthetic rubber, urethane rubber, and silicone rubber can be used. There is no particular limitation on the moisture resistant resins 61b and 62b, but moisture resistant resins such as epoxy resins, acrylic resins, and polyimide resins can be used. Hereinafter, the present invention will be described in more detail with reference to specific examples. An annular ultrasonic motor having a diameter of 50 mm, an inner diameter of 42 mm and a height of 5 mm as shown in FIG. 4a was constructed. In FIG. 4a, the vibrating portion 7 of the ultrasonic motor is provided on the surface of an annular piezoelectric ceramic 11 having a thickness of 0.3 mm on which an electrode 12 of a thickness of 1 μm made of an alloy is formed by vapor deposition. The back surface of the iron elastic body 2 having a circumferential arrangement of a large number of projection segments 21 is bonded and fixed using an adhesive 5 made of epoxy resin, and the other surface of the annular piezoelectric ceramic 11 on which the electrodes 12 are formed. Then, the exposed surface of the adhesive layer 5 is coated with a synthetic rubber paint to a thickness of 0.3 mm, applied and dried to form flexible resin layers 61a and 62a, respectively, and further formed on the upper layer. Using a coating made of a moisture-resistant epoxy resin, the coating was applied to a thickness of 0.2 mm and cured to form moisture-resistant resins 61a and 62b, respectively. Projection segment 2
Reference numeral 1 is provided to facilitate the mechanical vibration of the vibrating section 7 and increase the amplitude.
A friction material 4 made of composite plastic is adhered and fixed to the toroidal permanent magnet moving body 3 constituting the corresponding moving section 8. The vibrating part 7 and the moving part 8 are pressed by a magnetic force, and the surface of the protrusion 21 of the elastic body 2 and the friction material 4 are in contact. An external view of the piezoelectric element 1 is shown in FIG. 4b. On the surface of a piezoelectric ceramic 11, an electrode 12 formed by vapor deposition of gold is formed in a divided manner. In such an electrode arrangement, the electrodes are divided into two sets and connected, the phase is changed by 90 degrees with time, a resonance frequency of about 30 KHz, and a power of 40 V of the piezoelectric material are input, so that seven waves in the circumferential direction are formed. A traveling wave is excited. The output characteristics of the thus obtained ultrasonic motor at 24 ° C. and 60% RH are as follows.
The no-load rotation speed was 200 rpm, and the starting torque was 600 gf-cm. Also, 40
When the device was driven under no load for 200 hours in a high humidity atmosphere at 90 ° C. and 90% RH, no abnormality such as leakage of the electrode portion, stop of the motor, peeling or cracking of the piezoelectric element was observed. Further, the output characteristics thereafter were measured at 24 ° C. and 60% RH. As a result, the output characteristics were the same as those at the initial stage, and no deterioration of the output characteristics was observed. On the other hand, in the above-described ultrasonic motor configuration, the ultrasonic motor in which the surface of the piezoelectric element on which the electrodes are formed is not covered with the flexible resin layer and the moisture-resistant resin layer is 40%.
The electrode was leaked at a place driven in a high humidity atmosphere of 90 ° C. and 90% RH, and the ultrasonic motor stopped driving. An ultrasonic motor in which the surface of an adhesive portion is not covered with a flexible resin layer and a moisture-resistant resin layer, when driven in a high humidity atmosphere of 40 ° C. and 90% RH, after about 80 hours, has a piezoelectric element. The adhesive between the metal and the elastic metal was peeled off, and the piezoelectric ceramic was cracked, so that the ultrasonic motor could not be driven. As is clear from the above Examples and Comparative Examples, the surface of the piezoelectric ceramic on which the electrodes are formed and / or the surface of the adhesive layer between the piezoelectric element and the metal elastic body are covered with a flexible resin layer. In addition, by covering the upper layer with a moisture-resistant resin layer, in a high-humidity atmosphere, there is no insulation failure between the electrodes, and excellent in moisture-resistant reliability, such as deterioration of adhesive strength and breakage of the piezoelectric ceramic do not occur. An ultrasonic motor can be obtained. Effect of the Invention As is apparent from the above description, the present invention provides a method in which the surface of a plate-shaped piezoelectric element on which an electrode is attached and formed is covered with a flexible resin, or is covered with a flexible resin. After that, by further covering with a moisture-resistant resin layer, in the high humidity atmosphere, the infiltration of water between the electrode portion and the electrode is suppressed, and the electrode insulation performance of the electrode portion is improved, It is possible to obtain an ultrasonic motor having a small variation in resonance frequency and excellent in moisture resistance reliability such as no cracks in the resin. Further, the surface of the adhesive between the piezoelectric element and the metal elastic body may be covered with a flexible moisture-resistant resin, or may be covered with a flexible resin and then further covered with a moisture-resistant resin layer. By configuring, in a high humidity atmosphere, since the intrusion of moisture into the adhesive portion is suppressed, deterioration of the adhesive force and cracking of the piezoelectric body are reduced, and
It is possible to obtain an ultrasonic motor having a small variation in resonance frequency and excellent in moisture resistance reliability such as no cracks in the resin.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 and 3 are enlarged cross-sectional views of a main part of an ultrasonic motor according to the present invention, and FIGS. 2 and 4 are perspective views illustrating an embodiment of the present invention. FIG. 5 is an operation explanatory view showing the principle of the ultrasonic motor. 1 piezoelectric element, 11 piezoelectric ceramic, 12 electrode, 2, 21 vibrator, 3 moving body, 4 friction material, 5 adhesive, 6, 61, 62, 61a, 6
1b, 62a, 62b: flexible moisture-resistant resin, 7: vibrating section, 8: moving section.

Claims (1)

Claims: (1) A traveling wave is generated on a surface of a plate-shaped piezoelectric element which is polarized in a predetermined direction and has electrodes formed in a predetermined shape, and one surface of which is fixedly adhered to a metal elastic body. In an ultrasonic motor configured to include an ultrasonic vibrating body and a moving body that is in pressure contact with the vibrating body, and that drives the moving body through a frictional force between the vibrating body and the moving body, The surface of the plate-shaped piezoelectric element on which is formed is coated with a moisture-resistant resin that has flexibility that can be deformed in response to vibration of the vibrator and that suppresses intrusion of moisture. Ultrasonic motor. (2) an ultrasonic vibrator for generating a traveling wave on a surface of one side of a plate-shaped piezoelectric element which is polarized in a predetermined direction and has electrodes formed in a predetermined shape, which is adhered and fixed to a metal elastic body; An ultrasonic motor configured to drive the moving body through frictional force between the vibrating body and the moving body, wherein the piezoelectric element and the metal The surface of the adhesive part with a body is coated with a moisture-resistant resin that has flexibility that can be deformed in response to vibration of the vibrating body and that prevents moisture from entering. Sound wave motor. (3) an ultrasonic vibrator that generates a traveling wave on a surface formed by adhering and fixing one surface of a plate-shaped piezoelectric element that is polarized in a predetermined direction and has electrodes formed in a predetermined shape to a metal elastic body; In an ultrasonic motor configured to include a moving body that is in pressure contact with the vibrating body and that drives the moving body through a frictional force between the vibrating body and the moving body, The surface of the piezoelectric element and the surface of the adhesive portion between the piezoelectric element and the metal elastic body have flexibility such that the surface can be deformed in response to the vibration of the vibrating body, and the penetration of moisture is suppressed. An ultrasonic motor coated with a moisture-resistant resin. (4) The ultrasonic motor according to any one of claims 1 to 3, wherein the resin has a two-layer structure in which a lower layer is a flexible resin and an upper layer is a moisture-resistant resin.