JP2999570B2 - Ultrasonic motor drive control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates relates to a drive control method for an ultrasonic motor, a driving control method for an ultrasonic motor <br/> over data that enables adjusting the braking force at the time of stop.

[0002]

2. Description of the Related Art In general, an ultrasonic motor moves an output surface of a stator so as to draw a Lissajous figure by combining torsional vibration and longitudinal vibration, and a rotor that contacts the output surface with a predetermined pressing force. Is formed to rotate.

When stopping the rotor, both the torsional vibration and the longitudinal vibration of the stator are stopped, and the frictional force generated between the output surface of the stator and the rotor is stopped as a braking force.

[0004]

However, according to the conventional braking method, since the braking force applied to the rotor is constant from the start to the end of the braking, the rotor stops suddenly, and the rotor stops. There is a problem that an inertial force acts when the rotor is stopped, and the rotor and a driven body connected to the rotor receive the inertial force and vibrate.

In particular, since the ultrasonic motor is used as a driving source for precision driving of the driven body, various adverse effects occur when the driven body vibrates when the motor is stopped. For example, in order for the driven body to start the next operation, it is necessary to wait until the vibration stops, which lowers the operation efficiency. If another operation is performed before the vibration stops, the driven body cannot be precisely driven.

[0006] The present invention has been made in view of these points, the braking force at the time of stop can be freely adjusted,
Ultrasonic mode that can prevent sudden stop of the rotor
It is an object of the present invention to provide a driving control method for a motor .

[0007]

[MEANS FOR SOLVING THE PROBLEMS] To achieve the above object
The drive control method for an ultrasonic motor according to the present invention includes a stator having a torsional vibration piezoelectric element for generating torsional vibration and a longitudinal vibration piezoelectric element for generating longitudinal vibration, and a stator that is brought into contact with the output surface of the stator. When stopping the ultrasonic motor having a rotatable rotor, while stopping the energization to the torsional vibration piezoelectric element, driving the longitudinal vibration piezoelectric element at the resonance frequency of the torsional vibration piezoelectric element, At this time, a braking force is applied to the rotor by consuming power generated in the torsional vibration piezoelectric element by a load resistance.

[0008]

By operating the ultrasonic motor according to the drive control method of the present invention, when the rotor of the ultrasonic motor is stopped, the electric power generated in the piezoelectric element for torsional vibration is consumed by the load resistance, thereby controlling the rotor. Power is applied and the rotor stops slowly.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 1 shows an embodiment of an ultrasonic motor driven by the present invention .

The ultrasonic motor 1 is formed by a cylindrical stator 2 and a disk-shaped rotor 3. A torsional vibration piezoelectric element 4 that generates torsional vibration is provided in a middle part of the stator 2 in the axial direction. A voltage of a predetermined frequency is applied to the torsional vibration piezoelectric element 4 from a drive power supply circuit 5 connected via a switching element 9. A piezoelectric element 6 for longitudinal vibration that generates longitudinal vibration is provided at the upper end of the stator 2. A voltage of a predetermined frequency is applied to the vertical vibration piezoelectric element 6 from a drive power supply circuit 7. The upper surface of the vertical vibration piezoelectric element 6 is an output surface 2 a of the stator 2. The rotor 3 is brought into contact with the output surface 2a while being pressed with a pressing force such as a spring force. A load resistor 8 for power consumption is connected to an electric terminal of the torsional vibration piezoelectric element via a switching element 9.

Next, the operation of the ultrasonic motor of this embodiment will be described together with the drive control method of the present invention.

In order to rotate the rotor 3, the movable contact piece 9a of the switching element 9 is supplied to the driving power supply circuit 5 side so that one driving power supply circuit 5 and the other driving power supply circuit 7
And a driving voltage having a predetermined frequency is applied to each of the piezoelectric vibrating elements, torsion vibration is generated by one of the piezoelectric elements 4 for torsional vibration, and longitudinal vibration of the same frequency as that of the torsional vibration is generated by the other piezoelectric element 6 for vertical vibration. Then, the rotor 3 is rotated by moving the output surface 2a so as to draw a Lissajous figure.

When the rotor 3 is stopped, the movable contact piece 9a of the switching element 9 is applied to the load resistor 8 to stop the power supply by one drive power supply circuit 5, and the other drive power supply circuit 7 A drive voltage having a frequency that causes the longitudinal vibration piezoelectric element 6 to longitudinally vibrate at the same frequency as the resonance frequency of the torsional vibration piezoelectric element 4 is applied to the longitudinal vibration piezoelectric element 6. As a result, the output surface 2a of the stator 2 abuts intermittently on the rotating rotor 3 at the frequency of the longitudinal vibration, and receives the frictional force with the rotor 3 to cause the stator 2 to rotate at the frequency of the longitudinal vibration, that is, for the torsional vibration. The torsional vibration occurs at the resonance frequency of the piezoelectric element 4. The torsional vibration of the stator 2 causes the torsional vibration piezoelectric element 4 to torsionally vibrate. Electric power is generated by the power generation action, and the electric power is consumed by the load resistor 8.

As described above, according to the present embodiment, a part of the kinetic energy of the rotor 3 is converted into electric energy by the power generating action of the torsional vibration piezoelectric element 6, and the electric energy is consumed by the load resistor 8. Therefore, the braking force due to the friction between the rotor 3 and the output surface 2a of the stator 2 is reduced, and the rotor 3 stops gently.

The operation during braking will be described with reference to FIGS.

FIG. 2A shows a braking characteristic based on a relationship between the number of rotations of the rotor and time, and FIG. 2B shows a torsion when the electric resistance in the driving power supply circuit 5 is the load resistance 8. The input / output characteristics of the vibrating piezoelectric element 4 are shown. In the figure, the solid line shows the case of this embodiment, and the broken line shows the case where both the piezoelectric elements 4 and 6 are stopped and braked based on the conventional method. .

As shown in FIG. 2A, in the conventional example, the rotation speed of the rotor 3 decreases linearly from the braking start time t0 and stops at the time t1. On the other hand, according to the present embodiment, it can be seen that the rotation speed of the rotor 3 gradually decreases at least in the form of a quadratic curve, and stops extremely slowly at time t2.

As shown in FIG. 2 (b), when the energization is stopped at time t0, in the conventional example, the fall of the input power in the driving power supply circuit 5 by the torsional vibration piezoelectric element 4, that is, the power generation is extremely small. A little was recognized. On the other hand, according to the present embodiment, a large fall of the input power is recognized,
It can be seen that power is generated by the torsional vibration piezoelectric element 4, and the generated power is gradually consumed by time t3.

According to FIG. 2A, although the stop time t2 of the rotor 3 according to the present embodiment is later than the stop time t1 of the conventional example, the time required for the vibration to settle due to the sudden stop of the conventional example is added. Then, the stop time of the genuine rotor 3 of the conventional example is much later than the stop time t2 of the present embodiment, and the superiority of the present embodiment becomes clear.

Furthermore, in the present embodiment, the braking force can be adjusted by changing the resistance value of the load resistor 8 to adjust the amount of power generated by the torsional vibration piezoelectric element 4.

That is, as shown in FIG. 3, FIG.
When the resistance of the driving power supply circuit 5 is changed as the load resistance 8 and the resistance is changed, the B-line without the resistance value has a higher rotational speed than the A-line with the resistance value. Declined slowly.

As described above, according to this embodiment, when the rotor 3 of the ultrasonic motor 1 is stopped, the torsional vibration piezoelectric element 4
Is consumed by the load resistor 8, a braking force is applied to the rotor 3, and the rotor 3 stops slowly. In addition, the braking force of the rotor 3 can be adjusted by freely adjusting the braking force.

Although the switching element 9 is shown in FIG. 1 as a symbol, its operating characteristics are good when formed by an electronic circuit using a semiconductor element.

Further, the present invention is not limited to the above-described embodiment, but can be modified as needed.

[0026]

Since, according to the invention the drive control method of the ultrasonic motor according to the present invention in this way is to act configured, it is possible to freely adjust the braking force at the time of stop, prevent sudden stop of the rotor This makes it possible to obtain an ultrasonic motor having extremely high reliability as a driving source for precision driving.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of an ultrasonic motor to which a drive control method according to the present invention is applied .

FIG. 2A is a characteristic diagram showing a braking characteristic based on a relationship between the number of rotations of a rotor and time, and FIG. Characteristic diagram showing input / output characteristics of

FIG. 3 is a characteristic diagram showing a braking characteristic when a value of a load resistance is changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 2 Stator 2a Output surface 3 Rotor 4 Piezoelectric element for torsional vibration 6 Piezoelectric element for longitudinal vibration 8 Load resistance 9 Switching element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-228275 (JP, A) JP-A 2-142367 (JP, A) JP-A-61-116980 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) H02N 2/10-2/16

Claims (1)

(57) [Claims] 1. A torsional vibration pressure for generating torsional vibration.
It has an electric element and a piezoelectric element for longitudinal vibration that generates longitudinal vibration.
And the output surface of this stator
Stop the ultrasonic motor with the rotatable rotor
When energizing the piezoelectric element for torsional vibration,
And the piezoelectric element for longitudinal vibration is
The device is driven at the resonance frequency of the element,
Power generated by the element is consumed by the load resistance.
And applying a braking force to the rotor.
Drive control method for ultrasonic motor.