JP2011155761A - Vibrator friction contact member for ultrasonic motor and vibrator for ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vibrator for an ultrasonic motor, which has a continuous initial operation by the shape of a friction contact portion at the tip of a vibrator, and capable of maintaining stably speed, thrust force and a stable resonant frequency, and of obtaining stable operation characteristics for long time. <P>SOLUTION: There are provided the friction contact member of the vibrator 1 for the ultrasonic motor for driving a driven body 2 by frictional contact, wherein a contact of the tip of the vibrator is made of a pin-shaped member in which the outer shape of a cross section and the cross sectional area keep the same state along an axial direction in abrading the contact by frictional contact with the driven body; and the vibrator for the ultrasonic motor, which is equipped with the friction contact member for the vibrator for the ultrasonic motor. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a vibrator for an ultrasonic motor, and more particularly to a structure of a friction contact portion at the tip of a vibrator that drives a driven body by friction contact.

With the rapid development of electronic and information technology, there is a need for further miniaturization and higher integration of precision parts, and ultra-precision positioning equipment that supports nano-order (10 ^-9 m) inspection and ultra-fine processing. Is required. In medical and bio-research, the development of applied technology by controlling proteins and cells has progressed, and the need for a microscope stage capable of positioning in a finer region is increasing. Furthermore, in recent years, along with the demand for higher accuracy, as the objects for inspection, processing, measurement, etc. become smaller, the positioning device and its drive source are also required to be smaller and lighter.

  As a drive device that copes with such a fine region in the nano-order, an ultrasonic motor using a piezoelectric vibration element as described in Patent Documents 1 to 3 has been developed in place of a conventional electromagnetic motor. In these patent documents, as will be described later, the material, hardness, wear resistance, and the like of the friction contact at the tip of the vibration element that makes frictional contact with the driven body are described in detail.

  This ultrasonic motor is a driving device based on a driving principle that is completely different from that of an electromagnetic motor, and has excellent features such as low speed, high torque, silence, and retention when stopped. Further, since the structure of the vibrator is simple, it is advantageous for downsizing and is expected as a small actuator.

  In general, an ultrasonic motor is composed of a vibrator and a moving body (driven body), and functions in a state where the frictional contact portion of the vibrator is pressed against the moving body and pressurized. In this state, an elliptical motion is generated in the frictional contact portion of the vibrator, so that the frictional contact portion intermittently presses the moving body and sends the moving body in one direction. The moving speed of the moving body is controlled by changing the amplitude of the elliptical motion.

JP-A-5-252767 Japanese Patent Laid-Open No. 2002-27768 JP 2005-124377 A

  Ultrasonic motors need to have stable operating characteristics. For this purpose, selection of the material and shape of the frictional contact portion at the tip of the vibrator that transmits the elliptical motion of the vibrator to the driven body is particularly important. However, conventionally, only the material of the friction contact portion is considered, and detailed attention is not paid to the shape and structure of the friction contact portion. Even if the contact portion has excellent wear resistance, the operating characteristics may vary depending on its shape, and the movement speed, thrust stability, and resonance frequency stability may be impaired.

  For example, when the frictional contact portion is composed of a hemisphere, if the hemisphere wears out after long-term use, the contact area with the driven body increases from the initial state, the resonance frequency increases, and the speed decreases or the operation stops. Cause the situation. Further, when the frictional contact is constituted by a rectangular body having a ridge such as a prism, chipping may occur due to the contact of the ridge, and the initial operation due to wear of the ridge is not maintained, resulting in a short life. Furthermore, if the area of the frictional contact portion is too large, the wear on the contact surface is not even and the operability is deteriorated. Conversely, if the area of the frictional contact portion is too small, the progress of wear is rapid and short. End of life.

  In Patent Document 1, the friction contact portion at the tip of the vibrator is made of a wear-resistant steel material such as stainless steel, and the driven body is made of alumina ceramic, zirconia ceramic, or other wear-resistant ceramic material, Although the structure with improved wear resistance is described, as shown in FIG. 2 of the document 1, the contact portion at the tip of the vibrator is a hemisphere, and the contact area changes due to contact wear as described above. .

  Also in Patent Document 2, although measures are taken for reducing the amount of wear such as the material, surface roughness, mechanical strength of the pressing member (friction contact portion) at the tip of the vibrator, the shape of the pressing member is mentioned. Only members with 90 ° ridges are shown. Even in Patent Document 3, although it is shown that the friction member is made of alumina, a composite material of alumina and titanium carbide, zirconia, or the like, the wear resistance is improved. It is a hemisphere and has the same problem as Patent Document 1.

  Therefore, according to the present invention, the vibration for an ultrasonic motor that maintains the stable speed, thrust, and stable resonance frequency by the shape of the frictional contact portion at the tip of the vibrator, maintains a stable speed, thrust, and stable resonance frequency, and provides stable operating characteristics over a long period. The challenge is to provide a child.

  According to the present invention, (1) in a frictional contact member of a vibrator for an ultrasonic motor that drives a driven body by frictional contact, when the contact at the tip of the vibrator is worn by frictional contact with the driven body. A vibrator frictional contact member for an ultrasonic motor, characterized in that it is constituted by a pin-shaped member that maintains the same cross sectional area and cross sectional area along the axial direction.

  According to the invention, (2) the pin-shaped member has a circular shape with a cross section of a diameter of 0.3 mm or more and 1.0 mm or less, and a length of 0.3 mm or more and 2.0 mm or less. The vibrator frictional contact member for an ultrasonic motor according to (1) is provided.

  According to the present invention, (3) the pin-shaped member has a rectangular shape with a side cross-section of 0.3 mm to 1.0 mm and a length of 0.3 mm to 2.0 mm. The vibrator friction contact member for an ultrasonic motor according to (1), wherein the rectangular ridge portion is rounded.

  According to the present invention, (4) the pin-shaped member is provided on a pin base at the tip of the vibrator, and the pin base is a columnar or prismatic shape having a diameter of 1 mm or more. The vibrator friction contact member for ultrasonic motors described in 1) is provided.

  Furthermore, according to the present invention, there is provided (5) an ultrasonic motor vibrator comprising the ultrasonic motor vibrator frictional contact member according to any one of (1) to (4).

According to the present invention, even after the frictional contact portion at the tip of the vibrator in the ultrasonic motor vibrator is frictionally worn, the shape in which the contact area with the driven body is constant makes it possible to achieve super stable operation characteristics. A vibrator for a sonic motor can be realized.
Further, chipping at the ridge portion of the frictional contact portion does not occur, progress of wear and damage are suppressed, and an ultrasonic motor vibrator having a long life can be realized.

It is the top view (A) and side view (B) of the vibrator for ultrasonic motors by Example 1 of the present invention. (A)-(c) is a perspective view which shows the state which abrasion progresses with the friction contactor (pin-shaped member) of the front-end | tip of a vibrator | oscillator shown in FIG. It is the top view (A) and side view (B) of the vibrator for ultrasonic motors by Example 2 of the present invention. It is a figure which shows the operating principle of the ultrasonic motor to which this invention is applied typically. (A)-(c) is a top view which shows the abrasion progress state of the vibrator | oscillator of the prior art example which comprised the friction contactor of the vibrator | oscillator tip with the hemisphere. It is an enlarged plan view of a prismatic pin-shaped member according to Embodiment 3 of the present invention. It is the figure which showed the relationship between the moving distance of the to-be-driven body in an ultrasonic motor, and the resonance frequency by comparing this invention with the vibrator of a prior art example.

  Next, the ultrasonic motor according to the embodiment will be described with reference to the drawings. FIG. 4 is a diagram schematically showing the operating principle of an ultrasonic motor to which the present invention is applied. This ultrasonic motor includes a vibrator 1 and a slider (driven body) 2, and the vibrator 1 is composed of a piezoelectric vibration element. By applying an electrode (not shown) provided on this side surface, the expansion and contraction operation and bending are performed. The motions are generated at the same time, and at least a part of the motion, in particular, the tip of the vibrator that is in frictional contact with the driven body 2 performs an elliptical motion to move the driven body 2 intermittently. For example, the point p (center point of the left end face of the vibrator) in FIG. 4A draws a locus shown in FIG. 4B through the four states (a) to (d). In the figure, x is an axis in the longitudinal direction of the vibrator, and y is an axis perpendicular to the upper and lower side surfaces 1a of the vibrator.

  A friction contact 3 is fixed (adhered) to the tip portion of the vibrator 1 that is elliptically moving. The elliptical motion of the vibrator 1 is transmitted to the driven body 2 through the friction contact 3 and becomes a driving force for moving the driven body 2. In the example of FIG. 4, the driven body 2 is sent downward along the guide 4 by repeating this elliptical motion. Further, if the driven 2 is formed in an annular shape, a rotational motion around the guide 4 can be generated. The magnitude of the elliptical motion is controlled by the input voltage to the electrode of the piezoelectric vibration element 1.

  Next, the present invention will be specifically described with reference to various examples.

  FIG. 1 is a plan view (A) and a side view (B) of a vibrator for an ultrasonic motor according to a first embodiment of the present invention, and FIG. 2 is a friction contact (pin-shaped member) 6 at the tip of the vibrator shown in FIG. It is an expansion perspective view which shows the pin stand 5, and has shown the state from which the wear of the pin-shaped member 6 progresses from (a) to (c) of the figure by continuing use. As shown in FIG. 1, a pin base 5 is provided at the tip of the vibrator 1, and a pin-shaped member 6 that is in frictional contact with the driven body is provided on the upper surface of the pin base 5.

  The pin-shaped member 6 of the first embodiment is formed in a columnar shape whose cross section has the same outer diameter along the axial direction. Therefore, even if the pin-shaped member 6 is worn by frictional contact with the driven body and the wear progresses from the initial state (a) to (b) and (c) as shown in FIG. Just by decreasing, the contact area with the driven body does not change, so that the initial operation is continued and stable speed, thrust, and resonance frequency are maintained. The pin-shaped member 6 provided on the pin base 5 may be fixed to the pin base 5 by an adhesive means, or may be formed integrally with the pin base 5.

  FIG. 5 is a plan view showing a state of progress of wear of a conventional vibrator in which the friction contact 3 at the tip of the vibrator is formed of a hemisphere. As wear progresses from the initial state (a) to (b) and (c), the area of the contact portion 3a with the driven body increases in a flat shape, and the resonance frequency increases and the speed gradually decreases as the area increases. Will eventually stop.

  The cylindrical pin-shaped member 6 of Example 1 according to the present invention has a pin diameter of 0.3 mm or more and 1.0 mm or less, preferably 0.5 mm or more and 0.8 mm or less. When the diameter of the pin-shaped member 6 exceeds 1 mm, the contact surface is too large, and the wear at the tip of the pin is not uniform throughout, resulting in poor operability. On the other hand, when the pin diameter is smaller than 0.3 mm, the wear progresses quickly and the life is shortened.

The length of the pin-shaped member 6 is preferably 0.3 mm or more and 2 mm or less. When the length exceeds 2 mm, the pin-shaped member 6 is easily broken by the stress applied to the base of the pin, and vibration of the pin itself is generated, so that the positioning accuracy of the ultrasonic motor is lowered.
Moreover, by making the cross-section of the pin-shaped member 6 circular, the directivity of contact with the driven body is eliminated, the degree of freedom in setting is increased, and mass productivity is also excellent.

  In the first embodiment, the pin base 5 to which the pin-shaped member 6 is fixed as shown in FIG. 1 is formed in a circular shape with a cross section of 1 mm or more in diameter. When the diameter of the pin base 5 is 1 mm or less, the pin base 5 easily falls off the vibrator 1 due to the bending stress of the adhesive surface with the vibrator 1.

  FIG. 3 is a plan view (A) and a side view (B) of the ultrasonic motor transducer according to the second embodiment of the present invention. In this case, the pin table 5 at the tip of the vibrator has a rectangular cross section. As an example, the rectangular pin base has a short side length of 2 mm and a long side length of 3 mm. The rectangular pin base 5 may have a square cross section. In this case, the length of one side of the square cross section is preferably 1 mm or more like the cylindrical pin base.

  The pin-shaped member may be a prism having a rectangular cross section. FIG. 6 is an enlarged plan view of the prismatic pin-shaped member 7. In this case, the ridges of the four side portions 7a of the prism are chamfered. The length of one side of the prism in this embodiment may be substantially the same as the diameter of the cylindrical pin-shaped member described above. In the case of a prismatic shape, the pin length is preferably 2 mm or less. When the chamfer is not chamfered at the ridge of the prism, chipping occurs at the ridge during frictional contact, wear is accelerated at this part, the initial operation is not maintained, and the service life is shortened. Thus, it was confirmed that such a problem does not occur.

  FIG. 7 is a diagram showing a change in the resonance frequency when the movement of the driven body proceeds, comparing the friction contact according to the present invention and the conventional friction contact. In the figure, a is a conventional hemispherical friction contact having a radius of 2 mm, and b is a conventional friction contact having a predetermined length of a cylindrical body having a radius of 2 mm divided along the axial direction. And c is a contact of a cylindrical pin-shaped member having a transverse cross section with a diameter of 0.8 mm according to the present invention. In the case of the semi-cylinder, the divided surface of the cylinder is fixed to the tip of the vibrator. In this example, the vibrator side contactor and driven body are formed of partially stabilized zirconia. As can be seen from this figure, the resonance frequency suddenly increases from around 1000 m in the case of a hemisphere and from around 500 m in the case of a semi-cylinder, whereas the cylinder with a constant cross-sectional area according to the present invention. In the pin-shaped member, the resonance frequency is substantially constant over substantially the entire movement range, and the operating characteristics of the ultrasonic motor are stable.

  As the material of the pin-shaped member in the present invention, various types of alumina ceramics and other wear-resistant members can be employed. For example, when an engineering plastic, particularly PPS is used, the driven body is preferably partially stabilized zirconia or 96% alumina or more. Further, when ceramic is selected as the material of the pin-shaped member, it is desirable that the pin-shaped member is partially stabilized zirconia and the driven body side is 96% or more alumina.

1 vibrator 2 driven body (slider)
5 Pin base 6 Cylindrical pin-shaped member 7 Prismatic pin-shaped member

Claims (5)

  In a frictional contact member of an ultrasonic motor vibrator that drives a driven body by frictional contact, when the contact at the tip of the vibrator is worn by frictional contact with the driven body, the outer shape of the cross section along the axial direction A vibratory friction contact member for an ultrasonic motor, characterized by comprising a pin-shaped member that maintains the same cross-sectional area.   2. The vibration for an ultrasonic motor according to claim 1, wherein the pin-shaped member has a circular cross section with a diameter of 0.3 mm or more and 1.0 mm or less and a length of 0.3 mm or more and 2.0 mm or less. Child friction contact member.   The pin-shaped member has a rectangular shape with a lateral cross-section of 0.3 mm or more and 1.0 mm or less, a length of 0.3 mm or more and 2.0 mm or less, and the ridge portion of the rectangle is chamfered. The vibrator friction contact member for an ultrasonic motor according to claim 1.   The vibrator friction contact member for an ultrasonic motor according to claim 2 or 3, wherein the pin-shaped member is provided on a pin base at a tip portion of the vibrator, and the pin base has a cylindrical shape or a prism shape with a diameter of 1 mm or more.   An ultrasonic motor vibrator comprising the ultrasonic motor vibrator frictional contact member according to claim 1.

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