JPH07110144B2 - Ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a small motor used in electronic devices and the like, and more particularly to an ultrasonic motor that generates high torque at low speed rotation.

(Prior Art) An ultrasonic motor has features such as low rotation, high torque, stop holding force, and low electromagnetic noise, compared with conventional electromagnetic motors. It is being considered for power motors for autofocus and automobiles. Various types of ultrasonic motors have been devised, but basically, a piezoelectric vibrator that produces elliptical vibration is used as a stator, and a rotor pressed against the piezoelectric vibrator causes a rotary motion via a frictional force. The three main methods will be introduced below.

FIG. 4 is a diagram showing a first example of a conventional ultrasonic motor. In this figure, a ring-shaped piezoelectric ceramic 42 in which two sets of divided electrodes are formed is attached to a metal ring, and high-frequency signals having different phases are applied to the two sets of electrode groups to advance a bending mode running in the circumferential direction on the upper surface of the ring. Generate waves. Each point makes an elliptic motion on the ring surface, and when the rotor 43 is brought into pressure contact with this, a torque is generated in this rotor in the direction opposite to the traveling direction of the wave motion.

FIG. 5 is a diagram showing a second example of the conventional ultrasonic motor. In this figure, a bolt-tightening oscillator 51 that causes torsional vibration and a laminated piezoelectric displacement element 53 are combined, and the combination of the movements of the two produces an elliptical motion at the tip of 53 and produces torque in the rotor 54 that presses against 53. is there.

FIG. 6 is a diagram showing a third example of a conventional ultrasonic motor. In this figure, piezoelectric ceramics are adhered to the four faces of a square rod made of an elastic body having a square cross section, and when a piezoelectric ceramics facing each other is applied with a high-frequency electric field of the same phase in a direction in which the piezoelectric ceramics expands in one direction and contracts in the other, it becomes tangential. The bending vibration can be independently generated in the two directions. The basic resonance of bending vibration under the condition that both ends are free has two nodes 0.224 and 0.776 from the end face when the total length is 1, and this part can be supported. When the frequency of the high-frequency voltage applied to the two sets of electrodes is set to the fundamental resonance frequency of bending vibration and the phases are shifted by π / 2, the antinodes at both ends and the center are shown in FIG. 6 (b).
Make a circular motion (elliptic motion) as indicated by the arrow. Therefore, a rotary motion can be obtained by directly contacting the rotor 65 with this end portion or by attaching a disc having a constant diameter. The feature of this structure is that it is easy to manufacture a bending oscillator that makes an elliptic motion.

(Problems to be Solved by the Invention) In order to obtain as high a torque as possible using the method shown in FIG. 1, 1) increase the radius of the rotor that is in contact with the end face that causes elliptical vibration.

2) Increase the torque by simultaneously utilizing the elliptical vibration of both ends and the center antinode.

Etc. are required. If the driving principle shown in FIG. 6 is used to realize these, the structure shown in, for example, the fourth example shown in FIG. 7 is obtained, but the small size characteristic of the ultrasonic motor is impaired. Therefore, a structure that meets the requirements of 1) and 2) and does not impair the small size characteristics is required.

Therefore, a technical object of the present invention is to provide an ultrasonic motor having a small size and a simple structure.

(Means for Solving the Problems) According to the present invention, a rod-shaped piezoelectric vibrator having a first cross section orthogonal to the central axis and having first and second end portions facing each other and performing elliptical vibration. And is orthogonal to the axis of rotation, and
Opening in a second cross-section larger than the first cross-section,
A rotor having a hole having first and second edges opposed to each other, the piezoelectric vibrator being inside the hole, the central axis being inclined with respect to the rotation axis, and the first An ultrasonic motor is provided, which is arranged so that the first and second ends are in contact with the first and second edges, respectively, and converts the elliptical vibration into rotational movement of the rotor.

[Operation] In the ultrasonic motor of the present invention, the rod-shaped piezoelectric vibrator is
The center axis of the rod-shaped piezoelectric vibrator and the rotation axis of the rotor intersect,
Furthermore, the first and second opposing piezoelectric rod oscillators
Are arranged so that the ends thereof contact the first and second edges of the rotor hole, respectively.

The elliptical vibrations of the first and second ends of the rod-shaped piezoelectric vibrator, which obtain the maximum torque, contact the first and second edges of the rotor hole and are converted into rotation about the rotation axis of the rotor. It

(Example) Hereinafter, the ultrasonic motor of the present invention will be described in detail.

FIG. 1 is a sectional view showing an ultrasonic motor according to an embodiment of the present invention.

In this figure, an ultrasonic motor includes a piezoelectric vibrator 1 having a circular cross section orthogonal to the central axis, jigs 2 and 2 ′ for fixing nodes of vibration of the piezoelectric vibrator 1, and a cup-shaped rotor 3.
And a support tool 6 that supports the rotor 3 via a ball bearing 5 so as to be rotatable about a rotation axis 4.

The piezoelectric vibrator excites elliptical vibration having the maximum amplitude at the opposing first and second ends 1a and 1b with a voltage having a predetermined frequency.

The cup-shaped rotor 3 has an opening at one end and a protrusion serving as a rotation axis at the other end, and the opening is wider than the cross section of the piezoelectric vibrator 1 and formed in a ring shape thicker than the central portion of the rotor. It has a part that is.

The ring portion 3a has a first inner edge 3b from the inside of the cup and a second inner edge 3c opposite it,
The first and second edges are respectively formed with tape surfaces having an inclination with respect to the rotating shaft 4.

The piezoelectric vibrator 1 is arranged in the opening, and the first and second ends 1a and 1b of the piezoelectric vibrator are in contact with the first and second edges, respectively.

FIG. 2 is a diagram showing the basic configuration of the ultrasonic motor according to the embodiment of the present invention. In this figure, 1 is a piezoelectric vibrator as a stator, and 3a is a ring portion 3a of the rotor. Since the ends of the piezoelectric vibrator 1 vibrate in an elliptical direction including a circle in the same direction facing each other, the piezoelectric vibrator 1 and the first inner edge 3b and the second inner edge of the ring portion 3a
The two contact points 3e and 3f of 3b can generate torque to the ring in the same direction, and both ends of the piezoelectric vibrator 1 can be used. Also, both ends 1a of the piezoelectric vibrator 1 and
Since 1b alternately applies a driving force to the ring portion 3a, the rotation can be smoothed.

FIG. 3 is a diagram schematically showing the operation of the ultrasonic motor according to the embodiment of the present invention.

In this figure, the piezoelectric vibrator 1 is orthogonal to the rotation axis 4,
Moreover, the rotary shaft 4 and the central axis 1c are arranged to intersect with each other in a hole having a cross section larger than the cross section orthogonal to the central axis 1c of the piezoelectric vibrator. Both ends 1a and 1b of the piezoelectric vibrator 1 are
An elliptical vibration as shown by the broken line 11 and the solid line 12 is performed, the first end 1a of which is at the first inner edge 3b of the ring portion and the second end 1b is at the second inner edge of the ring portion. Touching 3c. The contact portions are located symmetrically to each other with respect to the center O.

Next, an ultrasonic motor having a shape as shown in Table 1 was manufactured. Table 2 shows the characteristic values of the obtained ultrasonic motor.

[Effects of the Invention] As described above, in the ultrasonic motor of the present invention, the shape of the piezoelectric vibrator for generating the driving force is simple, and the shape of the piezoelectric vibrator is simple, and the piezoelectric vibrator It is possible to use both ends of the rotor as a driving force, and it is possible to use a rotor having a relatively large diameter for the bending oscillator, and thus a large torque can be obtained.

Further, since the center axis of the piezoelectric vibrator and the rotation axis of the rotor intersect at an angle of 0 ° or more, the length of the rotor in the rotation axis direction can be shortened and the volume as a whole is increased. I won't.

Furthermore, since both ends of the bending oscillator alternately apply the driving force to the rotor, the rotating force is smooth.

It has become possible to provide an ultrasonic motor having the above advantages.

[Brief description of drawings]

FIG. 1 is a sectional view showing an ultrasonic motor according to an embodiment of the present invention, FIG. 2 is a perspective view showing a basic configuration of an ultrasonic motor according to an embodiment of the present invention, and FIG. 4 is a perspective view showing a first example of a conventional ultrasonic motor, FIG. 5 is a perspective view showing a second example of a conventional ultrasonic motor, and FIG. 6A is a perspective view showing a third example of a conventional ultrasonic motor, FIG. 6B is a diagram for explaining the operation of the ultrasonic motor of FIG. 6A, and FIG. It is a perspective view which shows the 4th example of a sound wave motor. In the figure, 1 is a piezoelectric vibrator, 1a and 1b are end portions, 1c is a central axis,
2, 2'is a fixing jig, 3 is a cup-shaped rotor, 3a is a ring portion, 3b and 3c are edges, 3e and 3f are contacts, 4 is a rotating shaft, 5 is a ball bearing, 6 is a support tool, 41 is Piezoelectric ceramics ring, 42, 42 'divided electrode group, 43 metal ring, 44, 44' electric terminal, 45 rotor, 51 piezoelectric ceramic element for torsion oscillator, 52 and 52 'metal block for resonance, 53 is a laminated piezoelectric actuator, 54 is a rotor, 61
Is an elastic rod, 62 is a piezoelectric ceramic element, 63 is a disk for driving end, 64 and 64 'are jigs for supporting nodes, 65 is a rotor, and 66, 67 and 68 are in contact with antinodes of each vibration. , 69 is a shaft, 71 is a bending oscillator, and 72 and 72 'are node fixing supports.

Claims (1)

[Claims] 1. A rod-shaped piezoelectric vibrator having a first cross section orthogonal to a central axis and having first and second end portions opposed to each other and performing an elliptical vibration; A rotor having a hole having a second cross section larger than the first cross section and having first and second edges with respect to each other; The axis is inclined with respect to the rotation axis, and the first and second ends are arranged to contact the first and second edges, respectively, and the elliptical vibration is applied to the rotational movement of the rotor. An ultrasonic motor characterized by conversion.