JP3141209B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small motor used for OA equipment and toys, and more particularly to an ultrasonic motor having a large torque for a small rotor diameter.

[0002]

2. Description of the Related Art Generally, an ultrasonic motor has advantages such as a high torque at a low rotation speed, a stop holding force, and a small electromagnetic noise as compared with an electromagnetic motor. Used for auto focus and power motors for automobiles.

FIG. 5 is a perspective view showing a configuration example of a conventional ultrasonic motor. In FIG. 5, the piezoelectric torsional composite vibrator 1
01 and a single longitudinal torsional composite vibrator 1 including a piezoelectric longitudinal vibrator 102
The rotor 10 rotatably supported on one end face of the rotor 03
4 is brought into pressure contact.

FIG. 6 is a perspective view showing an example of the configuration of a piezoelectric torsional composite vibrator 101 used in the ultrasonic motor of FIG. In FIG. 6, a plurality of sector-shaped piezoelectric ceramic plates 105 polarized in the direction of a chord are joined in a disk or ring shape so that the directions of polarization are closed.

FIG. 7 is an explanatory view of the operation principle of the vertical one-torsion type ultrasonic motor. In FIG. 7, a vertical one-torsion composite vibrator 1
3 shows a state of a torsional vibration displacement ξ and a longitudinal displacement ξ ′ of the longitudinal direction and a rotation state of the rotor 104. The direction of each displacement is point symmetric as shown in FIG. 7, and has a vibration mode that becomes gradually larger as moving to both ends.

[0006]

As can be seen from FIG. 6, the conventional piezoelectric torsional composite vibrator 101 has a plurality of fan-shaped piezoelectric ceramic plates 105 bonded to each other. There is a disadvantage that the characteristics vary greatly. In general, in a columnar vibrator as shown in FIG. 5, since the resonance frequency of torsional vibration and the resonance frequency of longitudinal vibration do not match, the longitudinal vibration is non-resonant even when driven at the resonance frequency of torsional vibration. Is driven in the state described above. Therefore, there is a disadvantage that the vibration amplitude of the longitudinal vibration becomes small and it is difficult to increase the torque of the ultrasonic motor.

Accordingly, it is an object of the present invention to provide an ultrasonic motor which can reduce the diameter of a rotor and which is small and has a large torque.

[0008]

According to the present invention, there is provided a torsional vibrator made of a piezoelectric ceramic hollow cylinder which performs torsional vibration in a circumferential direction, and has a long end having one end opposed to one end of the torsional vibrator. A vertical vibrator made of a piezoelectric ceramic hollow cylinder that expands and contracts in the vertical direction, and a rotor interposed between the torsional vibrator and the vertical vibrator and pressed against one end of each vibrator. The characteristic ultrasonic motor is obtained.

According to the present invention, in the ultrasonic motor, the other end opposite to the one end of the longitudinal vibrator is fixed, and the torsional vibrator is supported by a node of torsional vibration. The characteristic ultrasonic motor is obtained.

[0010] According to the present invention, in the ultrasonic motor, a shaft that penetrates the longitudinal vibrator, the torsional vibrator and the rotor disposed therebetween in a straight line is provided, and the torsional vibrator is provided with a torsional vibration. An ultrasonic motor is obtained, wherein the ultrasonic vibrator is supported by a support ring at a node, and the other end of the longitudinal vibrator facing the one end is fixed to a fixing member and housed in the fixing frame.

According to the present invention, in the ultrasonic motor, the torsional longitudinal vibrator is provided on the outer peripheral surface of the piezoelectric ceramic hollow cylinder by a cross finger extending in a direction parallel to the longitudinal direction at 45 ° to the longitudinal direction. An ultrasonic motor characterized by having electrodes formed thereon is obtained.

According to the present invention, in the ultrasonic motor, the vertical vibrator is formed with interdigital electrodes extending in the length direction or in the circumferential direction on the outer peripheral surface of the piezoelectric ceramic hollow cylinder. Thus, an ultrasonic motor is obtained.

[0013]

In the ultrasonic motor according to the present invention, when the length of one of the longitudinal vibrators increases in synchronism with the displacement of the torsional vibrator, the rotor interposed therebetween is sandwiched between the two vibrators to reduce the torsional displacement. Rotate in the direction. At this time, the other longitudinal vibrator is contracted, and when the direction of the torsional displacement is reversed, the length of the longitudinal vibrator is extended in synchronization with the displacement of the torsional vibrator, and the rotor has the same torsional displacement direction as the previous rotational direction. To rotate.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an ultrasonic motor according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing one configuration example of the ultrasonic motor of the present invention. In FIG. 1, the ultrasonic motor is a so-called vertical vibrator torsion vibrator press-contact type ultrasonic motor.
A piezoelectric torsional vibrator in which two parts fixed respectively to 1.11 '(the other is 8') are opposed to each other at the other end, and a contact of torsional vibration is fixed between these end faces by a support ring 10. The rotor 6 is configured to sandwich the rotor 6 with two rotors 12, 12 'interposed therebetween. The rotors 12, 12 'are rotatably supported between both end faces of the torsional vibrator 6 and end faces of the piezoelectric longitudinal vibrators 8, 8'.

A shaft 13 which rotates integrally with the rotors 12 and 12 'penetrates the inside of the piezoelectric ceramic hollow cylindrical vertical vibrator and the torsional vibrator, and the whole is accommodated in a fixed frame 16, and at least one of the fixed frames 16 is provided. It is pressed by a nut 15 from the end via a disc spring 14.

FIG. 2 is a perspective view showing the torsional vibrator 6 used in the ultrasonic motor of FIG. In FIG. 2, oblique electrodes 6a, 6b,... Extending in the direction of 45 ° with respect to the length direction of the cylindrical column are formed on the outer peripheral surface of the hollow cylindrical column 7, and the conductive portions at opposite ends are formed. Are connected to the connecting portions 26a and 26b of the male and female terminals to form two terminals, forming an oblique interdigital electrode. These electrodes are formed by a general method of printing electrodes on a hollow piezoelectric ceramic cylinder. When a polarization process is performed using these oblique electrodes 6a and 6b, the polarization direction becomes a direction perpendicular to the length direction of the oblique electrodes 6a and 6b. When an AC voltage is applied to the diagonal interdigital electrodes in a state where the polarization is applied, if the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, stretching strain occurs in the direction of the polarization, and the polarity of the voltage is the polarity at the time of the polarization. In the opposite case, shrinkage strain occurs in the direction of polarization. When elongation or contraction occurs in the polarization direction, contraction or elongation occurs in the direction perpendicular to the polarization direction. Therefore, torsional displacement occurs in the piezoelectric ceramic hollow cylinder 7 such that both end faces are rotated in opposite directions and twisted.

FIG. 3 is a perspective view showing an example of the structure of one longitudinal vibrator 8 used in the ultrasonic motor of the present invention, and another longitudinal vibrator 8 'has the same structure. The peripheral electrodes 8a, 8b,... Are formed on the outer peripheral surface of the piezoelectric ceramic hollow cylinder 9 of FIG.
8a and another common portion (not shown) to form two terminals to form interdigital electrodes 17. When a polarization process is performed using the cross electrode 17, the polarization direction is perpendicular to the length direction of the cross finger electrode 17. When an AC voltage is applied to the interdigital electrode 17 in this state, when the polarity of the voltage is the same as the polarity of the voltage at the time of polarization, an elongation strain occurs in the direction of the polarization, and the polarity of the voltage is opposite to the polarity at the time of the polarization. In this case, shrinkage strain occurs in the direction of polarization. Therefore, the piezoelectric ceramic hollow cylinder 9 expands and contracts in the length direction.

Returning to FIG. 1, when the length of the vertical vibrator 8 is increased in synchronization with the displacement of the torsional vibrator 6, the rotor 12 is sandwiched between the respective end faces of the two vibrators 6, 8 and twisted. Rotate in the direction of displacement. At this time, the other longitudinal vibrator 8 'is contracted, and when the direction of the torsional displacement is reversed, the length of the longitudinal vibrator 8' is extended in synchronization with the displacement of the torsional vibrator 6, and the rotor 12 'is rotated in the previous rotational direction. It rotates in the same direction of torsional displacement as. In this case, when the driving frequency is constant, the rotation speed and the torque are determined by the amplitudes of the torsional vibration and the longitudinal vibration.

In the ultrasonic motor of the present invention shown in FIG. 1, since the torsional vibrator 6 and the longitudinal vibrator 8 (8 ') are independent, the respective resonance frequencies make the size of each vibrator independent. The resonance frequency can be matched by adjusting to. Therefore, the torsional vibrator 6 and the longitudinal vibrator 8 (8 ') can be driven at their respective resonance frequencies, and the vibration amplitude of the torsional vibration and the vibration amplitude of the longitudinal vibration can be increased. Further, by driving a longitudinal vibration having a high resonance frequency with respect to torsional vibration at １ ／ λ, a longitudinal vibrator having a resonance frequency that is shorter than the torsional vibrator and has a resonance frequency that matches the resonance frequency of the torsional vibration is obtained. The rotation direction of the rotors 12 and 12 'can be changed by changing either the phase of the torsional vibration drive voltage or the phase of the longitudinal vibration drive voltage by 180 °.

In the above embodiment of the present invention, the longitudinal oscillator 8
As the structure (8 '), the interdigital electrodes 8a, 8b, 8 are formed on the outer peripheral surface of the hollow piezoelectric ceramic column 9 in a direction parallel to the circumferential direction.
.. have been described, FIG.
As shown in FIG. 4 (b), a vertical vibrator may be formed by applying interdigital electrodes 18 on the outer peripheral surface of the hollow piezoelectric ceramic column 40 in a direction parallel to the length direction of the column. Further, as shown in FIG. The same effect can be obtained even when a piezoelectric longitudinal vibrator is formed by forming electrodes on substantially the entire outer peripheral surface and inner peripheral surface of the piezoelectric ceramic hollow cylinder 40 '.

[0021]

As described above, in the ultrasonic motor according to the present invention, the shape of the piezoelectric vibrator for generating the driving force is simple, and it is easy to use the generally used press molding technique. A piezoelectric torsional vibrator and a piezoelectric longitudinal vibrator can be obtained by applying electrode printing, which is also a common technique, to this outer peripheral surface using a piezoelectric ceramic hollow cylinder that can be manufactured. It is possible to provide an ultrasonic motor with less variation in characteristics due to a bonding step and a complicated processing step.

Further, in the ultrasonic motor of the present invention,
Since the resonance frequencies of the piezoelectric torsional vibrator and the piezoelectric longitudinal vibrator can be independently adjusted and matched, the vibration amplitude of each can be increased. Therefore, an ultrasonic motor having a large torque can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one configuration example of a vertical vibrator torsional vibrator press contact type ultrasonic motor of the present invention.

FIG. 2 is a torsional vibrator 6 used in the ultrasonic motor of FIG.
FIG.

FIG. 3 is a longitudinal oscillator 8 used in the ultrasonic motor of FIG. 1;
It is a perspective view which shows (8 ').

FIGS. 4A and 4B are perspective views showing a structural example of another type of vertical vibrator used in the ultrasonic motor of the present invention.

FIG. 5 is a perspective view showing a structure of a conventional ultrasonic motor.

FIG. 6 is a perspective view showing a structure of a piezoelectric torsional composite vibrator used in the ultrasonic motor of FIG.

FIG. 7 is an explanatory view of the operation principle of the vertical one-twist type ultrasonic motor of FIG. 5;

[Explanation of symbols]

 6 Torsional vibrator 7 Piezoelectric ceramic hollow cylinder 8 Vertical vibrator 8 'Vertical vibrator 8a Peripheral electrode 8b Peripheral electrode 8c Peripheral electrode 8d Peripheral electrode 8e Peripheral electrode 8f Peripheral electrode 8g Peripheral electrode 8h Peripheral electrode 10 Support ring 11 Fixed base 11' Fixed base 12 Rotor 12 'Rotor, 13 Shaft 14 Belleville spring 15 Nut 17 Cross finger electrode 18 Cross finger electrode 40 Piezoelectric ceramic 40' Piezoelectric ceramic 41a Cross finger electrode 41b Cross finger electrode 41c Cross finger electrode 41d Cross finger electrode 101 Piezoelectric torsion composite Vibrator 102 Piezoelectric longitudinal vibrator 102 'Piezoelectric longitudinal vibrator 103 Vertical one-twist composite vibrator 104 Rotor 105 Fan-shaped piezoelectric ceramic plate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 2/16

Claims (5)

(57) [Claims] 1. A torsional vibrator made of a hollow piezoelectric ceramic column that performs torsional vibration in a circumferential direction, and a piezoelectric ceramic hollow member having one end facing one end of the torsional vibrator and performing stretching vibration in the longitudinal direction. An ultrasonic motor comprising: a vertical vibrator formed of a cylinder; and a rotor interposed between the torsional vibrator and the vertical vibrator and pressed against one end of each vibrator. 2. The ultrasonic motor according to claim 1, wherein the other end of the longitudinal vibrator facing one end is fixed, and the torsional vibrator is supported by a node of torsional vibration. Ultrasonic motor. 3. The ultrasonic motor according to claim 1, further comprising: a shaft penetrating the longitudinal vibrator, the torsional vibrator, and a rotor disposed therebetween in a straight line, and the torsional vibrator is a node of torsional vibration. An ultrasonic motor, wherein the ultrasonic vibrator is supported by a support ring at a portion, and the other end of the longitudinal vibrator facing the one end is fixed to a fixing member and housed in the fixing frame. 4. The ultrasonic motor according to claim 1, wherein said torsional longitudinal vibrator extends on an outer peripheral surface of said piezoelectric ceramic hollow cylinder in a direction parallel to a longitudinal direction at an angle of 45 °. An ultrasonic motor characterized in that the ultrasonic motor is formed. 5. The ultrasonic motor according to claim 1, wherein said vertical vibrator has interdigitated electrodes formed on an outer peripheral surface of said piezoelectric ceramic hollow cylinder to extend in a length direction or in a circumferential direction in parallel. An ultrasonic motor characterized in that: