JP2006187161A - Ultrasonic motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic motor which is low cost, high torque and has high reliability. <P>SOLUTION: The motor is simplified by employing a simple phase power source circuit to achieve cost reduction, and longitudinal vibration is converted into a dimension direction vibration vector by applying groove machining having a predetermined angle to a stator 11, thereby providing a function as a motor. Also, the contact between the stator 11 and a rotor 12 is made fit with even and uneven structure to increase a contact area and a rigid mechanism is formed, thereby improving reliability. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an ultrasonic motor used as a kind of motor for rotation or linear motion.

  Ultrasonic motors have different operating principles from conventional electromagnetic motors, have no windings, have a simple structure, are small and low in speed, can provide high torque, have high responsiveness, no magnetic field lines, etc. It is expected to be used in many fields by taking advantage of its excellent features. In general, an ultrasonic motor is composed of a piezoelectric ceramic element, a stator, a rotor, and a rotating shaft. The piezoelectric ceramic element is composed of a complex electrode pattern so that a standing wave is generated, and a plurality of piezoelectric ceramic elements have a phase difference. It is arranged from pieces.

  As shown in FIG. 7, the groove angle of the stator is generally processed to 90 ° as disclosed in Patent Document 1, for example. As shown in FIG. 8, the contact angles of the stator and the rotor are generally in contact with each other on a horizontal plane as disclosed in Patent Document 2, for example. However, in these ultrasonic motors, torque reduction and rotation stoppage may occur due to wear between the stator and the rotor, and there are significant problems regarding performance and reliability.

JP-A-63-206176 JP-A-63-073887

  However, in order to drive the piezoelectric ceramic element and obtain a rotational motion, it is necessary to generate traveling waves in the piezoelectric element and the stator, rotate the rotor, and output the rotation to the shaft. For this purpose, the piezoelectric ceramic must be polarized into a complicated pattern, and a plurality of alternating voltages different by 90 ° must be applied. In a conventional ultrasonic motor drive circuit, two signals having different phases are independently amplified in two piezoelectric ceramic elements, so two sets of switching circuits and transformers are required. For this reason, there is a problem that the circuit itself becomes large, and the original advantage of the ultrasonic motor that the structure is simple cannot be utilized, which greatly affects the product cost.

  In order to eliminate these drawbacks, the present invention eliminates the conventional two-phase power supply with different phases, supplies only a single-phase single-circuit power supply, enables the drive power supply to be simplified, and generates a traveling wave. It is an object of the present invention to provide an ultrasonic motor that generates a rotation function without causing the rotation. It is another object of the present invention to provide an ultrasonic motor having a highly reliable structure with improved robustness as an ultrasonic motor.

  The present invention has been made as a result of studying the electrode structure of a piezoelectric ceramic and the configuration of an ultrasonic motor in order to solve the above problems.

  That is, the ultrasonic motor of the present invention has a structure in which a stator, a rotor, and a rotating shaft are combined as shown in FIG. 4, and a piezoelectric ceramic element is mounted on the stator as shown in FIG. It is united with. Hereinafter, it is simply referred to as a stator.

  In addition, in the spiral groove processing, by making an angle of 1 ° to 45 ° inward from the outer periphery of the stator and with respect to a horizontal plane, the longitudinal vibration of the piezoelectric ceramic element is changed to oblique vibration on the stator. By changing and generating a thrust force in the rotor, vibration in the thickness direction can be converted into circumferential propulsion. That is, as shown in FIG. 5, the vibration direction of the stator generates a force represented by the following formula as a rotational force Fθ with respect to the force F in the vibration direction.

  Fθ = F × cos (θ)

  This force causes a force in the direction of rotation to rotate the rotor. At this time, the rotor is transmitted to the main shaft 32 shown in FIG. 6 and a rotational motion is output to the outside. When the angle is greater than 45 °, the force Fθ in the rotational direction decreases, and in order to rotate the rotor, it is necessary to increase the force F in the vibration direction, which is not practical.

  When the stator and the rotor are in pressure contact with each other and have a contact angle of 1 ° to 45 ° with respect to the horizontal plane of the stator, the stator and the rotor have an uneven contact structure, and a thrust in the rotational direction is obtained in the stator. In addition, a wider contact area is obtained, and the robustness of the contact surface is increased and the reliability is improved. When the angle is larger than 45 °, the contact area between the stator and the rotor is reduced, and the reliability is lowered.

  Furthermore, the surface of the piezoelectric ceramic element has electrodes having different polarities or full-surface homopolar electrodes, and the electrode structure can be a radial structure, a spiral shape, or a simple structure in which the entire surface has an electrode structure. There is no need to polarize the piezoceramic element in a complicated pattern as disclosed in Document 1.

  Compared to the conventional ultrasonic motor having a piezoelectric ceramic electrode structure, the drive power supply circuit is simplified, and there are significant advantages in terms of cost, and it is possible to provide an ultrasonic motor that does not depend on the phase drive system.

  At the same time, by changing the vibration direction by changing the groove direction of the stator and changing the contact angle between the stator and the rotor, it is possible to provide an ultrasonic motor having a high robustness and a highly reliable structure.

  Next, embodiments of the ultrasonic motor according to the present invention will be described with specific examples.

  FIG. 1 is an example of a piezoelectric ceramic element used in the present invention. FIG. 1 (a) shows a radial electrode (4 divisions), FIG. 1 (b) shows a spiral electrode, and FIG. ) Indicates a full-surface electrode. In the present invention, the electrode divided into four electrodes as shown in FIG. 1 (a) is used, and each electrode is subjected to the same-polarization treatment (1, 3, 2, and 4). The electrodes 1 and 3 having the same polarity are short-circuited to the electrical terminal 1 in FIG. 6 and the electrodes 2 and 4 having the same polarity are electrically shorted to the electrical terminal 2 in FIG. . Further, the back side of the four divisions is a full-surface electrode, and is connected to a driving power source via a G terminal 36 in FIG. FIG. 6 shows a configuration diagram of a drive circuit that supplies power to the electrical terminals 34 and 35. The frequency for controlling the power supply to the electrical terminal 34 and the electrical terminal 35 is changed by switching the drive power supply (on and off). This electrical terminal transmits power to the alternating electrodes. Further, the structural resonance frequency is set appropriately so that the vibration amplitude of the stator is maximized.

  2 is a view showing a stator of an ultrasonic motor according to an embodiment of the present invention, FIG. 3 is a view showing a rotor, and FIG. 4 is an assembly view of the stator and the rotor. As shown in FIG. 2 (a), the stator has a plurality of spiral grooves, and the inner peripheral portion has a mortar-like concave shape. Further, the rotor is also convex and inclined at the same angle as the stator as shown in FIG. 3A, so that the concave portion of the stator and the convex portion of the rotor are fitted together.

  Table 1 shows the characteristics of the ultrasonic motor of the present invention.

  From the above, compared with the conventional ultrasonic motor, torque and efficiency were improved and durability was improved within the range of 1 ° to 45 °.

  The ultrasonic motor according to the present invention can be used for fine control of a rotary table by utilizing the performance of low speed and high torque, and can be used for a power window motor, a wiper motor and the like for automobiles. In addition, it can be expected to be used as a linear motor for robots for linear motion positioning.

The schematic diagram which shows the piezoelectric ceramic element shape and electrode pattern which concern on embodiment of this invention. Fig.1 (a) is a figure which shows a radial electrode (4-part dividing) pattern. FIG. 1B shows a spiral electrode pattern. FIG.1 (c) is a figure which shows a whole surface electrode pattern. The figure which shows the stator of the ultrasonic motor which concerns on embodiment of this invention. FIG. 2A is a plan view showing a stator. FIG. 2B is a front view showing the stator. The figure which shows the rotor of the ultrasonic motor which concerns on embodiment of this invention. FIG. 3A is a plan view showing the rotor. FIG. 3B is a front view showing the rotor. The assembly drawing of the stator and rotor of an ultrasonic motor concerning an embodiment of the invention. The vector diagram showing the power of the stator of the ultrasonic motor concerning an embodiment of the invention. 1 is a drive power circuit block diagram of an ultrasonic motor according to an embodiment of the present invention. The figure which shows the stator of the conventional ultrasonic motor. FIG. 6 is a structural diagram of a conventional ultrasonic motor.

Explanation of symbols

1,3 electrodes (same polarity)
2, 4 electrodes (same polarity)
5, 6 Electrode 7 Piezoelectric ceramic element 11 Stator 12 Groove 13 Rotor 14 Spindle shaft 21 Piezoelectric ceramic element 22 Stator 23 Groove 31 Ultrasonic motor unit 32 Spindle shaft 33 Drive power supply 34, 35 Electrical terminal 36 G terminal 37 Switching 38 Amplifier 39 Oscillator 41 Spindle shaft 42 Bearing 43 Rotor 44 Stator 45 Piezoelectric ceramic element 46 Groove

Claims (4)

  An ultrasonic motor having a piezoelectric ceramic element, a stator, a rotor, and a rotating shaft, wherein the vibration direction of the piezoelectric ceramic element is changed by subjecting the stator to spiral groove processing. .   2. The ultrasonic motor according to claim 1, wherein the spiral groove has an angle of 1 ° to 45 ° from the outer periphery of the stator toward the inside and with respect to a horizontal plane.   The ultrasonic motor according to claim 1, wherein the stator and the rotor are in pressure contact and have a contact angle of 1 ° to 45 ° with respect to a horizontal plane of the stator.   2. The ultrasonic wave according to claim 1, wherein the surface of the piezoelectric ceramic element has electrodes having different polarities or full-surface homopolar electrodes, and the electrode structure has a radial shape, a spiral shape, or the whole surface has an electrode structure. motor.

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