JP2929224B2 - Ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a so-called ultrasonic motor using piezoelectric vibration of a piezoelectric vibrator used for OA equipment, cameras, etc., and particularly to a small-sized ultrasonic motor having a relatively large torque. It relates to the structure of the motor.

(Prior Art) FIG. 6 is a perspective view showing the structure of a conventional longitudinal-twist type ultrasonic motor, in which a piezoelectric torsional composite vibrator 101 and a piezoelectric longitudinal vibrator 1 are shown.
02, the bearing 104
The roller 105 is rotatably supported by a spring 106 and is brought into pressure contact with the spring 105.

FIG. 7 is a perspective view showing the structure of the piezoelectric torsional composite vibrator 101 used in the conventional longitudinal-twist type ultrasonic motor shown in FIG. In FIG. 7, four sector-shaped piezoelectric ceramic plates 107 polarized in the direction of the strings are aligned with the end face so that the directions of polarization are closed, as shown by the white arrows in FIG. Are joined.

8 (a) and 8 (b) are explanatory diagrams of the operation principle of the longitudinal-twist type ultrasonic motor of FIG.

FIGS. 8 (a) and 8 (b) show the torsional vibration displacement に お け る, the lengthwise expansion and contraction displacement ξ ′, and the rotational direction of the rotor 5 at positions along the respective axes of the longitudinal-torsional composite vibrator. Since the directions of the displacements are shown in FIG. 8, detailed description is omitted.

Assuming that the rotation direction indicated by the arrow 108 in FIG. 6 is the forward direction, as shown by the solid line 109 in FIG. 8 (a), in the forward direction, the torsional displacement ( The size of ξ) gradually increases, and both ends exhibit torsional displacements in opposite directions. On the other hand, also in the case of the reverse direction shown by the broken line 110 in FIG. 8 (a), the torsional displacement (ξ) becomes
It is symmetric with the forward direction.

The expansion and contraction displacement (ξ ') in the direction of the arrow 111 shown in FIG. 6 is, as shown by the solid line 112 in FIG. Becomes Conversely, as shown by the dashed line 113 in FIG. 8 (b), when one end side is contracted and the other end side is extended, the magnitude of the displacement (ξ ′) is similarly maximized at both ends.

(Problems to be Solved by the Invention) As can be seen from FIG. 6, in the conventional rotation conversion mechanism, one end of the rotor 105 is rotatably supported by the bearing 104 by the shaft 114, and the rotor pressure contact force is adjusted by the spring 106.
Therefore, there is a disadvantage that the state of contact between the rotor surface and the end face of the vibrator is not uniform, and so-called uneven rotation occurs in which the rotation becomes slower or faster.

Accordingly, a technical object of the present invention is to provide a small-sized ultrasonic motor having a relatively large torque by eliminating the above-mentioned disadvantages.

(Means for Solving the Problems) According to the present invention, there is provided a piezoelectric ceramic hollow cylinder having a central axis, at least one end of which is configured to perform longitudinal-torsional vibration, and the piezoelectric longitudinal-torsional vibrator. A support member provided at a node of vibration of the vibrator; a wear-resistant member layer provided at an end of the piezoelectric ceramic hollow cylinder which performs longitudinal-torsional vibration; and a rotatable member provided around the central axis. An ultrasonic motor having a ring-shaped rotor whose one end face is pressed against the wear-resistant member layer, wherein a fixing plate having a projection inserted into the inner diameter of the rotor; An elastic body interposed between the other end face opposing the one end face, and a spring member for pressing the fixed plate against the other end face of the rotor via the elastic body in the center axis direction. Sonic motor is obtained You.

According to the present invention, in the ultrasonic motor, the piezoelectric longitudinal-torsional vibrator is provided on a part of a peripheral surface of the piezoelectric ceramic hollow cylinder in a first crosswise direction in one of a circumferential direction and a longitudinal direction. A vertical vibrator formed by applying a finger electrode and being polarized using the first interdigital electrode, and a direction inclining with respect to the central axis direction on the remaining part of the outer peripheral surface of the piezoelectric ceramic hollow cylinder. And a torsional vibrator formed by using the second interdigital electrode and polarizing by using the second interdigital electrode.

According to the present invention, in any of the above-described ultrasonic motors, the ultrasonic motor is characterized in that the support member is provided at one end of the piezoelectric longitudinal-torsional vibrator.

(Operation) In the ultrasonic motor of the present invention, the protrusion of the fixed plate is inserted into the inner diameter surface of the rotor, and an elastic body is interposed. The fixed plate is pressed against the rotor in the axial direction by a spring. , Make uniform contact with the wear-resistant member layer,
The longitudinal-torsional vibration of the end face of the torsional vibrator is converted into uniform rotation of the rotor without rotation unevenness.

(Example) Hereinafter, an ultrasonic motor of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a half sectional view cut along the axial direction showing an example of the structure of the longitudinal-torsion type ultrasonic motor of the present invention. In FIG. 1, the end of the torsional vibrator of the longitudinal-torsional composite vibrator 10 is fixed with a support 13 including a first bearing 12 so that torsional vibration can be excited at 1/4 wavelength. A wear-resistant member layer 14 is formed on the end face of the rotor 10, a ring-shaped rotor 15 and an elastic body 16 are sandwiched, and a protruding portion 17a of a rotor fixing plate 17 is fitted into the rotor inner diameter 15a and pressed by a leaf spring 18. Have been. Therefore, in operation, the first bearing 12 and the second bearing 12
The shaft 20 and the rotor 15 penetrating through 19 rotate integrally.

FIG. 2 is a perspective view showing a structural example of the longitudinal-torsion composite vibrator 10 used in the ultrasonic motor of FIG. In FIG. 2, first interdigital electrodes 31a, 31a, which are perpendicular to the longitudinal direction, that is, parallel to the circumferential direction, around one end of the outer peripheral surface of the hollow columnar piezoelectric ceramic 11 formed by press molding.
31b is formed. The electrode 31a is connected by a connection electrode (not shown) provided in the length direction, while both the electrode 31b and the connection electrode 31b are connected by the connection electrode 32. These electrodes 31a, 31b, and 32 are formed by printing a paste containing a conductive material.

When the polarization process is performed using the intersecting circumferential electrodes 31a, 31b, and 32, the polarization direction becomes a direction perpendicular to the length direction of the first interdigital electrode. In this state, the first interdigital electrodes 31a, 31b, 31
When an AC voltage is applied to c, 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. Distortion occurs. As a result, the piezoelectric ceramic hollow cylinder
11 expands and contracts in the length direction. Further, the second interdigital electrode 33a, which is inclined by 45 ° with respect to the length direction, on the outer peripheral surface of the other portion of the piezoelectric ceramic hollow cylinder 11 where the first interdigital electrode is provided,
33b are formed. These electrodes 33a, 33b and 32 are formed by printing a paste containing a conductive material on the hollow column 11 of the piezoelectric ceramic.

Each of the second interdigital electrodes 33a, 33b is connected by common electrodes 33c, 33d provided along the circumferential direction. The common electrode 33c is the same as the lowermost portion of the first interdigital electrode 31a. These electrodes 33a, 33b, 33c, and 33
d is formed by printing a paste containing a conductive material on the piezoelectric ceramic hollow cylinder 11.

When the polarization process is performed by the second interdigital electrodes 33a and 33b, the polarization direction is perpendicular to the length direction of the second interdigital electrodes 33a and 33b. When an AC voltage is applied to the second interdigital electrodes 33a and 33b in this state, if the polarity of the voltage is the same as the direction of the polarization, an elongation strain occurs in the direction of the polarization, and the polarity of the voltage becomes the same as the direction of the polarization. In the opposite case, shrinkage distortion 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.

As a result, torsional displacement occurs in the piezoelectric ceramic hollow cylinder 11.

In addition, instead of the first interdigital electrodes 31a and 31b shown in FIG. 2, there are interdigital electrodes 51a and 51b provided along the length direction shown in FIG. Every other common electrode 5
2a, 52b, and a longitudinal vibrator subjected to polarization processing using the interdigital electrodes 51a, 52a, and shown in FIG. 3 (b).
The same effect as that of the longitudinal-torsional vibrator shown in FIG. 2 can be obtained even if one of the longitudinal vibrators having electrodes on the entire outer surface is formed.

FIG. 4 is a perspective view showing another structural example of the longitudinal-twist type ultrasonic motor of the present invention. In FIG. 2, a central node of vibration of the longitudinal-torsional composite vibrator 10 'is fixed by a support ring 21, and wear-resistant member layers 22, 22 ′ and a ring-shaped rotor 23,2
3 'and the elastic members 24, 24' are sandwiched therebetween, and the rotor fixing plates 25, 25 'having protrusions which can be fitted into the rotor inner diameters are pressed against each other by leaf springs 26, 26'. And the rotors 23, 23 'provided at both ends of the vibrator.
, And the rotors 23 and 23 ′ integrally rotate.

In these cases, the state of contact between the rotor surface and the end face of the vibrator is steadily and substantially uniform because the degree of freedom is generated between the end face of the vibrator and the rotor surface.

FIG. 5 is a perspective view showing a structural example of a longitudinal-torsion composite vibrator 10 'used in the ultrasonic motor of FIG. In FIG. 4, first interdigital electrode pairs 31a, 31b and 31a ', which are parallel or perpendicular to the longitudinal direction, around both ends of the outer peripheral surface of the piezoelectric ceramic hollow cylinder 11' formed by the press molding technique. 31b 'are respectively formed by printing.

2, the interdigital electrodes 31a and 31b are connected by connecting electrodes 32 provided in the longitudinal direction, respectively.
Similarly, a 'and 31b' are connected by connection electrodes 32 'provided in the length direction, respectively.

When the polarization process is performed using the pair of first interdigital electrodes 31a, 31b and 31a ', 31b', the polarization direction is the same as the length direction of the first interdigital electrodes 31a, 31b and 31a ', 31b'. It is a right angle direction. In this state, the first interdigital electrode pairs 31a, 31b and 31
When an AC voltage is applied to a 'and 31b', elongation strain occurs in the direction of polarization when the polarity of the voltage is the same as the polarity of the voltage during polarization, and polarization occurs when the polarity of the voltage is opposite to the polarity during polarization. Shrinkage occurs in the direction of. As a result, the piezoelectric ceramic hollow cylinder 11 'expands and contracts in the length direction. Also, the first interdigital electrode pairs 31a, 31b and 3 of the piezoelectric ceramic hollow cylinder 11 '
Second interdigital electrodes 33a and 33b inclined by 45 ° with respect to the length direction are formed in a portion between 1a and 31b.

As in FIG. 2, each of the second interdigital electrodes 33a, 33b is formed by common electrodes 33c, 33c 'provided along the circumferential direction.
One end of one of the second interdigital electrodes 33a is connected to a common electrode 33c, and the other of the second interdigital electrodes 33b is connected to the other end opposite to the one end by a common electrode 33c '.

The common electrodes 33c, 33c 'are connected to the first interdigital electrodes 31a, 31.
It is the same as the central part of a '. When the polarization process is performed by the second interdigital electrodes 33a and 33b, the polarization direction becomes a direction perpendicular to the length direction of the second interdigital electrodes 33a and 33b.

When an AC voltage is applied between the second interdigital electrodes 33a and 33b in this state, when the polarity of the voltage is the same as the direction of the polarization, an elongation strain occurs in the direction of the polarization, and the polarity of the voltage becomes the same as the direction of the polarization. In the opposite direction, 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.

As a result of the above, the piezoelectric ceramic hollow cylinder 11 '
Causes torsional displacement.

The first interdigital electrodes 31a, 31b and 31a ', 31b' shown in FIG. 5 are shown in FIGS. 3 (a) and 3 (b), similarly to the piezoelectric longitudinal-torsional vibrator of FIG. A similar effect can be obtained by using a vertical vibrator.

(Effects of the Invention) 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 the ultrasonic vibrator can be easily formed by 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 the outer peripheral surface of a piezoelectric ceramic hollow cylinder that can be manufactured. Thus, an ultrasonic motor having a small variation in characteristics due to a bonding process and a complicated processing process can be obtained. Further, in the ultrasonic motor of the present invention, since the rotor surface and the end face of the vibrator are provided with a degree of freedom of surface contact, a small ultrasonic motor having a small load fluctuation, a very small rotation unevenness and a relatively large torque can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing one structural example of a longitudinal-twist type ultrasonic motor of the present invention, and FIG. 2 shows the structure of a piezoelectric longitudinal-torsion composite vibrator used in the ultrasonic motor of FIG. Figure, 3rd
4A and 4B are perspective views showing an example of the structure of another type of longitudinal vibrator used in the ultrasonic motor of the present invention. FIG. 4 is another perspective view of the longitudinal-twist type ultrasonic motor of the present invention. FIG. 5 is a partial sectional view showing a structural example. FIG. 5 is a perspective view showing a structural example of a piezoelectric longitudinal-torsion composite vibrator used in the ultrasonic motor shown in FIG.
FIG. 7 is a partial sectional view showing the structure of a conventional longitudinal-torsion type ultrasonic motor, FIG. 7 is a perspective view showing a structural example of a piezoelectric torsional composite vibrator used in the ultrasonic motor of FIG. 6, and FIG. (a) and (b) are explanatory diagrams of the operation principle of the longitudinal-twist type ultrasonic motor. In the figure, 12, 19 are bearings, 18, 25, 25 'are springs, and 10, 10' are vertical-
The torsional composite vibrator, 11 and 11 'are piezoelectric ceramic hollow cylinders, 1
3 is a support, 14, 22, 22 'is a wear-resistant member layer, 15, 23, 23' is a rotor, 16, 24, 24 'is elastic, 17, 25, 25' is a rotor fixing plate, 2
0 and 27 are shafts, 21 is a support ring, 31, 31b and 31a ', 31
b 'is the first interdigital electrode, 33a and 33b are the second interdigital electrodes, 3
2, 32 'are connection electrodes, 33c, 33c', 33d are common electrodes, 101 is a piezoelectric torsional composite vibrator, 102 is a piezoelectric vertical vibrator, 103 is a longitudinal-torsional composite vibrator, 104 is a bearing, 105 is a rotor, 106 is a spring, 107 is a piezoelectric ceramic plate, and 114 is a shaft.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-163982 (JP, A) JP-A-2-228275 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H02N 2/00

Claims (3)

(57) [Claims] 1. A piezoelectric ceramic hollow cylinder having a central axis, at least one end of which is provided with a piezoelectric longitudinal-torsional vibrator that performs longitudinal-torsional vibration, and provided at a node of vibration of the piezoelectric longitudinal-torsional vibrator. A support member provided, a wear-resistant member layer provided at an end of the piezoelectric ceramic hollow cylinder that performs longitudinal-torsional vibration, and an end surface provided at the wear-resistant member layer rotatably provided around the central axis. An ultrasonic motor having a ring-shaped rotor to be pressed into contact with a fixed plate having a protruding portion inserted into the inner diameter of the rotor, and a second end face facing the one end face of the fixed plate and the rotor. An ultrasonic motor, comprising: an interposed elastic body; and a spring member that presses the fixed plate against the other end surface of the rotor via the elastic body in the center axis direction. 2. The ultrasonic motor according to claim 1, wherein said piezoelectric longitudinal-torsional vibrator is provided on a part of a peripheral surface of said piezoelectric ceramic hollow cylinder in one of a circumferential direction and a longitudinal direction. A first interdigital electrode, and a vertical vibrator formed by polarization using the first interdigital electrode, and the remaining part of the outer peripheral surface of the piezoelectric ceramic hollow cylinder in the central axis direction. An ultrasonic motor comprising: a second interdigital electrode provided in a direction inclined with respect to the torsion transducer; and a torsional vibrator formed by polarization using the second interdigital electrode. 3. The ultrasonic motor according to claim 1, wherein said support member is provided at one end of said piezoelectric longitudinal-torsional vibrator.