JP2006262626A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor where a body to be driven will not rotate in the direction opposite to the moving direction, when reducing speed. <P>SOLUTION: The ultrasonic motor 1 has two ultrasonic vibrators 3, arranged in directions A1, A2 crossing at a prescribed angle, and a substantially V-shaped head member 4 for connecting the two ultrasonic vibrators 3. The head member 4 comprises two output reception sections 4c for receiving each output of the two ultrasonic vibrators 3; a composite section 4a for combining the outputs from the two output receiving sections 4c; and a neck section 4b, provided in between the two output receiving sections 4c and the combining section 4a. The ratio R (=S2/S1) of an axial cross-sectional area S1 of the output receiving section 4c to the minimum axial cross-sectional area S2 of the neck section 4b is set at 0.3≤R≤0.75. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic motor, and more particularly to an ultrasonic motor that prevents the reverse of the direction of movement of a driven body during deceleration and improves speed controllability in a low speed range.

  Two ultrasonic transducers, a holding member that holds these ultrasonic transducers at a predetermined angle (for example, 90 degrees), and a substantially V-shaped shape, the apex portion thereof being in contact with the driven body A resonance type ultrasonic motor having a head whose open end (the V-shaped open side) is connected to an ultrasonic transducer is known (for example, see Patent Document 1).

  An ultrasonic motor having such a structure has two natural vibration modes that vibrate in directions orthogonal to each other, and drives two ultrasonic vibrators at a resonance frequency that matches the two natural vibration modes. Thus, elliptical motion can be generated at the tip of the head. For example, by driving each ultrasonic transducer with a voltage having a resonance frequency whose phase is shifted by 90 degrees, an elliptical motion can be generated at the tip of the head.

  Therefore, for example, when the head is pressed against the slider attached to the linear guide with a constant force, the frictional force generated between the head and the slider gives the slider a thrust in the extending direction of the linear guide. It can be moved along the guide.

However, this ultrasonic motor has a problem that when the speed is decreased from the high speed side to the low speed side, a phenomenon that the moving direction of the slider is reversed occurs, which makes it difficult to precisely position the slider. Further, if the slider is stopped at such a speed that the reverse of the speed does not get angry, the slider is rubbed due to the inertia of the slider, and it is difficult to increase the positioning accuracy.
JP 2000-152671 A

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an ultrasonic motor that does not reverse the direction of movement of the driven body during deceleration.

That is, the present invention includes two ultrasonic transducers arranged in a direction intersecting at a predetermined angle;
Two output receivers for receiving the outputs of the two ultrasonic transducers;
One combining unit that combines the outputs from the two output receiving units;
Neck portions respectively provided between the two output receiving portions and the combining portion;
An ultrasonic motor comprising:
The ratio R (= S2 / S1) of the axial center cross-sectional area S1 of the output receiving portion and the minimum axial center cross-sectional area S2 of the neck portion is 0.3 ≦ R ≦ 0.75. To provide an ultrasonic motor.

  According to the present invention, it is possible to prevent the occurrence of speed reversal when the driven body is decelerated while using the conventional driving method due to the structure of the ultrasonic motor. Thereby, the outstanding effect that the positioning accuracy of a to-be-driven body can be raised is produced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view showing a schematic structure of the ultrasonic motor 1. The ultrasonic motor 1 connects the two ultrasonic transducers 3 with two Langevin type ultrasonic transducers 3 arranged in the directions of the axial centers A1 and A2 intersecting at a predetermined angle (90 degrees in FIG. 1). A substantially V-shaped head member 4 and a holding member 5 that holds the two ultrasonic transducers 3 are provided.

  Each of the two ultrasonic transducers 3 includes a piezoelectric element 6 that expands and contracts in the axial direction of each ultrasonic transducer 3 by applying a predetermined voltage. Each piezoelectric element 6 has an annular shape, and a bolt member 7 is inserted through a hole in the center thereof. Screw parts 7a and 7b are formed at both ends of the bolt member 7, respectively. The screw part 7a has a nut shape in which an outer surface is formed in a columnar shape and a screw part corresponding to the screw part 7a is formed inside. The housing 8 is screwed. Holes for inserting the bolt members 7 are also formed at both ends of the holding member 5.

  The head member 4 is in contact with an output receiving portion 4c constituting the open end side, a driven body (not shown), one combining portion 4a for combining outputs from the two output receiving portions 4c, and two outputs. And a neck portion 4b provided between the receiving portion 4c and the combining portion 4a.

  Each of the two output receiving portions 4c is formed with a screw portion corresponding to the screw portion 7b of the bolt member 7, and is screwed with the bolt member 7. Thus, by screwing the output receiving portion 4c of the head member 4 and the housing 8 to the bolt member 7, the holding member 5 can be fixed and the piezoelectric element 6 can be tightened with a predetermined force. Thus, the ultrasonic transducer 3 is configured.

  The output receiving portion 4c receives the output (vibration) of the piezoelectric element 6, and this vibration is transmitted to the synthesizing portion 4a through the neck portion 4b. The neck portion 4b plays a role as a mechanism for enlarging the displacement of the vibration of the piezoelectric element 6 received by the output receiving portion 4c. Thus, the vibrations generated in the two ultrasonic transducers 3 are magnified by the neck portion 4b and then synthesized by the synthesis unit 4a.

  As described above, the ultrasonic motor 1 has two natural vibration modes (vertical vibration mode and horizontal vibration mode shown in FIG. 1) that vibrate in directions orthogonal to each other. By driving the two ultrasonic vibrators 3 with voltages whose phase of the resonance frequency to match the two natural vibration modes is shifted by 90 degrees, elliptical motion can be generated in the combining unit 4a. When a slider or a rotor (not shown) is brought into contact, such a slider or the like receives a thrust from the combining portion 4a via a frictional force with the combining portion 4a, and moves or rotates in the direction of the thrust. Note that if the phase of the drive voltage for driving the two ultrasonic transducers 3 is reversed, the direction in which the driven body moves, rotates, etc. can be reversed.

  FIG. 2 shows an enlarged perspective view of the head member 4. In FIG. 2, as the output receiving portion 4c, the cross-sectional shape (transverse cross-sectional shape) orthogonal to the displacement direction of each piezoelectric element 6 (that is, the extending direction of the axes A1 and A2) is shown as a quadrangle. However, the cross-sectional shape of the output receiving portion 4c is not limited to this, and may be a circle or a polygon other than a rectangle.

  In FIG. 2, the neck portion 4b has a quadrangular cross-sectional shape. This is adapted to the shape of the output receiving portion 4c, but even if the shape of the output receiving portion 4c is a quadrangular prism shape, the neck portion 4b may have a conical constriction shape. For example, when the output receiving portion has a cylindrical shape, it is preferable that the neck portion has a circular shape as a cross-sectional shape.

  The axial center cross-sectional area of the output receiving portion 4c is normally constant, where the cross-sectional area is represented by “S1” and the minimum axial center cross-sectional area of the neck portion 4b is represented by “S2”. In the sonic motor 1, the ratio R (= S2 / S1) is set to 0.3 ≦ R ≦ 0.75.

  FIG. 3 is a graph showing an example of the speed control characteristic of the driven body when the ratio R is changed. Here, a 1.3 kg slider is used as the driven body, the driving frequency is about 31 kHz (the resonance frequency is shifted depending on the value of R, and the driving frequency is adjusted to this resonance frequency), and the phase difference is 90. The ultrasonic motor 1 was driven by changing the voltage values of the sine wave and cos wave, and the moving speed of the slider was measured.

  As a result, as shown in FIG. 3, it was confirmed that when R = 0.15, the slider can move at a high speed, but a phenomenon that the moving direction of the slider reverses during deceleration occurs. As a result of the test, when the R value is less than 0.3, a phenomenon in which the moving direction is reversed when the slider is decelerated appears, but this phenomenon becomes difficult to appear as the R value increases. When the R value is 0.3 or more, it is confirmed that the reversal of the moving direction when the slider is decelerated does not occur and the speed controllability during low-speed driving is improved. FIG. 3 shows the case of R = 0.4 and 0.6.

  As the R value increases, the displacement enlargement performance of the ultrasonic transducer 3 decreases. As shown in FIG. 3, it is confirmed that the slider speed decreases as the R value increases. It was done. When the R value exceeds 0.75, the two ultrasonic transducers 3 each have a large amount of flexural deformation caused by vibration received from the counterpart ultrasonic transducer, and the outer peripheral portion of the piezoelectric element 6 is missing. It was confirmed that (damage) occurred and the product life was shortened. Further, when the R value is increased, the vibration mode is changed due to an increase in the flexure of the ultrasonic transducer 3, and the speed control of the slider becomes difficult.

  The ultrasonic motor of the present invention is suitable for an XY stage feed mechanism or the like mounted on a semiconductor manufacturing apparatus or the like that requires precise speed control and positioning accuracy on a driven body.

Sectional drawing which shows schematic structure of an ultrasonic motor. The perspective view which expands and shows the head member of an ultrasonic motor. The graph which shows an example of the speed control characteristic of an ultrasonic motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Ultrasonic motor 3; Ultrasonic vibrator 4; Head member 4a; Synthesis | combination part 4b; Neck part 4c; Output receiving part 5; Holding member 6; Piezoelectric element 7; Bolt member 7a * 7b;

Claims (1)

Two ultrasonic transducers arranged in a direction intersecting at a predetermined angle;
Two output receivers for receiving the outputs of the two ultrasonic transducers;
One combining unit that combines the outputs from the two output receiving units;
Neck portions respectively provided between the two output receiving portions and the combining portion;
An ultrasonic motor comprising:
The ratio R (= S2 / S1) of the axial center cross-sectional area S1 of the output receiving portion and the minimum axial center cross-sectional area S2 of the neck portion is 0.3 ≦ R ≦ 0.75. Ultrasonic motor.

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