JP3218945B2 - Ultrasonic motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a rotor structure and a control circuit for an ultrasonic motor.

[0002]

2. Description of the Related Art In recent years, ultrasonic motors have attracted attention as next-generation actuators that take advantage of advantages such as higher torque per unit volume than electromagnetic motors.

This ultrasonic motor exhibits stable and maximum characteristics when a vibrating body that vibrates ultrasonically and a rotor that slides on the vibrating body are in uniform contact and uniformly pressurized.

FIG. 5 is a structural view of a conventional ultrasonic motor. In FIG. 5, 29 is a vibrating body, 30 is an output shaft, 31
Is a rotor integrally formed with the output shaft 30, and 32 is a rotor 3
A pressurizing spring 33 presses the vibrating body 29 with the pressurizing member 1, a pivot receiver 33 is pressed by the pressurizing spring 32 and contacts the end surface of the output shaft 30 to press the rotor 31, 34 is a metal bearing, 35 is a frame, 36 Is a bracket.

Conventionally, in order to uniformly contact and uniformly press these, a method of supporting and pressing the rotor and the vibrating body has been required to have high accuracy.

FIG. 6 shows a block diagram of a control circuit of an ultrasonic motor using a conventional rotor and having a vibration sensor on a vibrating body. In FIG. 6, reference numeral 21 denotes a variable frequency oscillation circuit;
Is a divider circuit and a 90 ° phase shifter, 23 is a power amplifier circuit,
24 is an ultrasonic motor, 25 is a vibration sensor on a vibrating body, 3
7 is a peak value detection circuit, and 38 is a comparison operation circuit. Conventionally, as shown in FIG. 6, only a peak value of a signal of a vibration sensor provided on a vibrating body is detected, and control is performed by operating the frequency of an oscillation circuit based on this information.

When the ultrasonic motor is driven, the contact surface between the rotor and the vibrating body is processed with high precision so as to draw a fixed trajectory in order to stabilize the rotation by frictional force and the control by the signal of the vibration sensor. Was needed. The signal of the stabilized vibration sensor indicates the vibration state of the vibrating body and does not include the actual rotation speed information of the rotor. Further, since only the peak value of this signal is used as measurement data, it has been difficult to accurately control the rotation speed.

The ultrasonic motor which has been subjected to such high-precision processing is vulnerable to external pressure, vibration, changes in the surrounding environment, and the like, and its characteristics are significantly degraded by changes in the contact state and the like.

[0009]

The contact surface of the rotor and the contact surface of the vibrating body need to be in uniform contact and pressurized uniformly, and each contact surface must be slid while maintaining a high degree of parallelism. The cost is high because the support structure needs to be movable.

Further, if the contact state between the rotor and the vibrating body changes due to external pressure, vibration, changes in the surrounding environment, etc., and the contact pressurization becomes non-uniform, the rotation speed fluctuates, the life is shortened, and the lock is reduced. May occur.

In an ultrasonic motor in which a vibration sensor is provided on a vibrating body, a locus drawn by a contact surface between the rotor and the vibrating body when the motor is driven is always constant so that disturbance of a signal from the vibration sensor does not occur. It is designed to be.
For this reason, there is a problem in that only the local portion where the rotor and the vibrating body are in contact with each other is worn by driving, and the contact state is quickly deteriorated, so that the life is shortened.

[0012]

Means for Solving the Problems To solve the above-mentioned problems, a structure which can follow the inclination of the contact surface when supporting the vibrating body has been used in the prior art. We propose a structure that can change the inclination of the surface.

In addition, the trajectory on the contact surface of the vibrating body, on which the rotor contact surface slides when the motor is driven, is reciprocated uniformly and radially at a constant cycle, and a vibration sensor is provided on the vibrating body. In the ultrasonic motor having the above, since the signal of the vibration sensor varies regularly depending on the position of the rotor, simple and more accurate speed control can be performed by detecting the signal having the position information.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an ultrasonic motor according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a vibrating body, 2 denotes an output shaft, and 3 denotes an output shaft 2. A second rotor in which the integrally formed first rotor 4 contacts the first rotor 3 and simultaneously contacts the contact surface of the vibrating body 1;
5 is a pressing spring for pressing the rotor against the vibrating body 1, and 6 is pressed by the pressing spring 5 to come into contact with the end face of the output shaft 2, and the first rotor 3, the second rotor 4 , A pivot receiver for pressurizing, a metal bearing 7, a frame 8, and a bracket 9. The surface where the first rotor 3 and the second rotor 4 are in contact with each other is formed as a part of a spherical surface, and the frictional force therebetween is the contact surface between the second rotor 4 and the vibrating body 1. The contact area, friction coefficient, and the like are taken into consideration so that the friction force between the first rotor 3 and the second rotor 4 does not increase due to the friction force between the first rotor 3 and the second rotor 4 due to the reaction of the driving force. It is designed to be put in.

(Embodiment 2) FIG. 2 shows a plan view and a cross-sectional view of a rotor according to a second embodiment. In FIG. 2, reference numeral 10 denotes a second rotor, and 11 denotes a first rotor. Is formed by a part of a spherical surface, and the first rotor 1
A mortar-shaped groove as shown in FIG. 2 is provided on at least one of the surfaces where the first and second rotors 10 are in contact with each other. Thereby, the slip between the first rotor and the second rotor due to the reaction of the driving force is reduced, and the inclination of the contact surface of the rotor follows the change in the inclination of the contact described in the first embodiment. Contact can be realized more smoothly, and the characteristics of the motor are stabilized.

(Embodiment 3) FIG. 3 shows the shape of a rotor and a vibrating body according to the present invention and a vibration sensor on a piezoelectric body adhered to the back surface of the vibrating body. In FIG. A contact surface where the rotor contacts the vibrator, 14
Is an output shaft, 15 is an elastic body that mechanically amplifies vibration, 16
Is a protrusion for amplifying the vibration amplitude on the elastic body 15, 17 is a contact portion of the rotor 12 at an arbitrary time on a surface where the elastic body 15 contacts the rotor 12, 18 is a piezoelectric body, and 19 is a rotor 12 of the piezoelectric body 18. Drive electrode on the surface opposite to
Is a vibration sensor on the surface opposite to the rotor 12. The elastic body 15 and the piezoelectric body 18 are fixed by bonding or the like to form a vibrating body. In the above configuration, by making the shape of the contact surface 13 of the rotor 12 a regular quadrangle, the rotor 1 can be uniformly and widely spread over the contact surface of the elastic body 15 when the motor is driven.
Since the second contact surface 13 slides, the surface to be worn is widely dispersed, and can withstand a long-time driving, thereby extending the life.

(Embodiment 4) Piezoelectric body 1 of Embodiment 3
FIG. 4 shows a speed control circuit diagram of an ultrasonic motor having the vibration sensor 20 of FIG. 21 is a frequency variable oscillation circuit, 22 is a frequency divider circuit and a 90 ° phase shifter, 23 is a power amplifier circuit, 24 is an ultrasonic motor, 25 is a vibration sensor on a vibrating body, 26 is a peak value detection circuit, and 27 is a phase detector. A detection circuit 28 is a comparison operation circuit.

By making the shape of the contact surface of the rotor a regular square as in the third embodiment, the contact surface of the rotor can be uniformly and temporally regulated over a wide range on the contact surface of the vibrating body when the motor is driven. , The vibration sensor generates a signal approximating a sine wave.

In FIG. 4, a peak value of a sine wave approximation signal from the vibration sensor is detected by a peak value detection circuit 26, and a phase shift amount is detected by a phase detection circuit 27.
The comparison operation circuit 28 performs a comparison operation with the peak value and the phase shift amount at the target rotational speed, and operates the drive frequency to control the speed.

When the apex of the regular square of the contact surface of the rotor is in contact with the position of the shortest distance from the vibration sensor, the outer peripheral portion having a large vibration amplitude of the vibrator is pressurized. The resonance frequency rises, the peak value of the signal of the vibration sensor approximated to a sine wave rises, and its phase is delayed. Conversely, when the midpoint of the regular quadrangular side of the rotor contact surface is in contact with the position of the shortest distance from the vibration sensor on the contact surface of the vibrator, the inner peripheral portion where the vibration amplitude of the vibrator is small As a result, the resonance frequency of the vibrating body viewed from the vibration sensor decreases, and the peak value of the signal of the vibration sensor approximated to a sine wave decreases, and the phase advances.

In an ultrasonic motor using a conventional rotor,
The signal from the vibration sensor provided on the vibrating body is only information on the vibration state of the vibrating body and does not include the position information of the rotor. However, by using the rotor of the present invention, the signal on the vibrating body depends on the position of the rotor. Since the peak value and phase shift amount of the signal from the vibration sensor vary regularly, simple and more accurate control can be performed by using the signal including the position information of the rotor.

[0023]

According to the first embodiment, the surface where the first rotor and the second rotor are in contact with each other is a part of a spherical surface, so that the shaft runout of the output shaft and the inclination of the contact surface of the vibrator can be achieved. , The inclination of the contact surface of the rotor follows the change, and stable contact can always be realized, so that the characteristics of the motor are stabilized.

A motor having a structure in which the center of the spherical surface where the first rotor and the second rotor contact each other is on the side of the pressure spring opposite to that of FIG. 1 and a structure in which the output shaft is supported by only one bearing. Similar effects can be obtained.

In the second embodiment, by providing a mortar-shaped groove on the spherical contact surface, slippage between the first rotor and the second rotor due to the reaction of the driving force can be reduced. As in the first embodiment, the inclination of the contact surface of the rotor follows the change in the inclination of the contact, so that stable contact can always be realized more smoothly, and the characteristics of the motor are stabilized.

In the third embodiment, the shape of the contact surface of the rotor is a regular square, so that the contact surface of the rotor slides uniformly over a wide range on the contact surface of the vibrating body when the motor is driven. The surface to be scattered is widely dispersed, and can withstand a long-time driving, and can have a long life.

In the fourth embodiment, as in the third embodiment, the shape of the contact surface of the rotor is a regular square,
Since the peak value and the phase shift amount of the signal from the vibration sensor on the vibrating body change regularly depending on the position of the rotor, simple and accurate control is performed by using the signal including the position information of the rotor. It becomes possible.

In the third and fourth embodiments, the shape of the rotor contact surface is not limited to a regular quadrangle but also a positive n.
The same effect can be obtained by using a square shape.

Also, since the surface accuracy of the surface of the contact surface of the rotor of the ultrasonic motor is extremely high, the contact surface is easily damaged in the assembling process, and the contact surface can be worn out by driving for a long time. Conventionally, the entire rotor has been replaced, but in the present invention, only the second rotor needs to be replaced, and the recyclability is excellent.

[Brief description of the drawings]

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

FIG. 2 is a plan and sectional view of a rotor according to a second embodiment of the present invention.

FIG. 3 is an exploded perspective view of a main part of a motor according to a third embodiment of the present invention.

FIG. 4 is a block diagram of a motor speed control circuit according to a fourth embodiment of the present invention.

FIG. 5 is a sectional view of a conventional ultrasonic motor.

FIG. 6 is a block diagram of a control circuit of a conventional ultrasonic motor.

[Explanation of symbols]

 1,29 vibrator 2,14,30 output shaft 3,11 first rotor 4,10 second rotor 5,32 pressure spring 6,33 pivot receiver 7,34 metal bearing 8,35 frame 9,36 bracket 12, 31 Rotor 13 Contact surface 15 Elastic body 16 Protrusion 17 Contact portion 18 Piezoelectric body 19 Drive electrode 20, 25 Vibration sensor 21 Variable frequency oscillation circuit 22 Divider circuit and 90 ° phaser 23 Power amplifier circuit 24 Ultrasonic motor 26 , 37 Peak position detection circuit 27 Phase detection circuit 28, 38 Comparison operation circuit

Claims (4)

(57) [Claims] 1. An ultrasonic motor comprising a vibrating body that vibrates ultrasonically and a rotor that slides on the vibrating body, wherein the rotor is composed of two parts, each of which is provided with a concave or convex spherical surface, The spherical portions are brought into pressure contact with each other,
An ultrasonic motor characterized in that output is taken out through frictional force between two parts. 2. The method according to claim 1, wherein at least one of the concave or convex spherical portions where the two portions constituting the rotor are in contact with each other has
2. The ultrasonic motor according to claim 1, wherein n radial grooves are provided in a radial direction from the output shaft. 3. An ultrasonic motor comprising: a vibrating body formed by fixing a piezoelectric body that vibrates ultrasonically and an elastic body that amplifies vibration; and a rotor that slides on the elastic body. An ultrasonic motor, wherein a contact surface of the rotor in contact with the rotor has a regular n-sided shape. 4. A vibrating body formed by fixing a piezoelectric body that vibrates ultrasonically and an elastic body that amplifies vibration, and a rotor that slides on the elastic body, wherein a vibration sensor is provided on the piezoelectric body. An ultrasonic motor comprising: an ultrasonic motor, wherein a shape of a contact surface of the rotor in contact with the elastic body is a regular n-gon, and speed control is performed using a signal of the vibration sensor.