JPH0793828B2 - Ultrasonic motor drive - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a drive device for an ultrasonic motor using ultrasonic vibration.

(Background of the Invention) An ultrasonic motor includes a stator 12 composed of an elastic body 9 and a piezoelectric body 10 as shown in FIG. 5, as disclosed in "Nikkei Meknical, No. 1983.2.28" issued by McGraw-Hill.
And a rotor 11. FIG. 4 shows a drive circuit for the ultrasonic motor shown in FIG. The piezoelectric body 10 of the ultrasonic motor is connected between the terminals LG of the piezoelectric body 10 and the terminal R.
It can be regarded as a capacitor having a capacitance between −G and each. When the piezoelectric body 10 of the stator 12 is excited at a specific frequency, a traveling wave having the same frequency is generated on the rotor side surface of the elastic body 9, and the rotor 11 is driven by this traveling wave.

The drive circuit of the ultrasonic motor shown in FIG.
And the coils 4L and 4R and the oscillator 5. The terminals L, G, R of the piezoelectric body 10 are connected to the terminals 5L, 5G, 5R of the oscillator 5, respectively, the coil 4L is provided between the terminals LG of the piezoelectric body 10, and the terminal RG of the piezoelectric body 10 is provided. Is connected to the coil 4R. The oscillator 5 is connected between terminals LG of the piezoelectric body 10 and terminals RG.
Two-phase alternating current with 90 ° different phases is generated, amplified and applied. The electrical resonance frequency of the ultrasonic motor is set by the capacitance component of the coil 4L and the terminal L portion of the piezoelectric body 10, and similarly the capacitance component of the coil 4R and the terminal R portion of the piezoelectric body 10. It When the electrical resonance frequency and the mechanical resonance frequency of the ultrasonic motor match, the traveling wave is generated.

In order to stop the ultrasonic motor, the supply of the two-phase alternating current from the oscillator 5 can be prohibited. But,
The ultrasonic motor is not stopped immediately by stopping the oscillator 5. Even if a motor stop signal is input to the ultrasonic motor to stop it, at least the piezoelectric body 10 retains electric energy equivalent to the capacitance component, so that the elastic body 9 is consumed until this energy is consumed. A traveling wave is generated on the surface of the rotor and the rotor 11 is rotated. Therefore, when the ultrasonic motor is stopped, there is a large difference between the position where the ultrasonic motor is stopped and the position where it is actually stopped. Is a major obstacle to its application.

(Object of the Invention) An object of the present invention is to solve the above problems and to provide an ultrasonic motor having good stopping characteristics without being affected by the electric energy remaining in the piezoelectric body during braking.

(Summary of the Invention) In order to achieve such an object, the present invention incorporates a consumption means into a drive device of an ultrasonic motor so that the electric energy remaining in the capacitance component of a piezoelectric body during braking is consumed by the consumption means. The technical point is to do this.

(Example) The Example of this invention is described using drawing. In the embodiment, the same parts as those in the conventional example described above are designated by the same reference numerals,
The description is omitted.

FIG. 1 shows a first embodiment of the present invention. In FIG.
The drive circuit of the ultrasonic motor includes braking resistors 3L and 3R and switching elements 2L and 2R (oscillator 5 that generates a two-phase alternating current).
And the coils 4L and 4R and the piezoelectric body 10.

A braking resistor connected in series between the electrodes LG of the piezoelectric body 10.
3L, switching element 2L, and coil 4L are connected in parallel, and similarly a braking resistor connected in series between electrodes RG.
3R, switching element 2R, and coil 4R are connected in parallel. These switching elements 2L and 2R are connected to the control circuit 6 of the ultrasonic motor. The consumption means of the present invention corresponds to the braking resistor and the switching element of the embodiment.

Switching element 2L, 2R when driving ultrasonic motor
Are both off, the braking resistors 3L and 3R do not function and form a normal drive circuit, and the two-phase alternating current from the oscillator 5 causes the electrostatic capacitance component of the piezoelectric body 10 and the coil 4L (4R). Formed by
When applied to the LC resonance circuit, the piezoelectric body 10 resonates to generate a traveling wave in the elastic body 9 to drive the rotor 11. However, when a motor stop signal is input from the control circuit 6 of the ultrasonic motor during braking of the ultrasonic motor, the oscillator 5
Immediately stops the generation of two-phase alternating current, and at the same time, the switching elements 2L and 2R are both turned on. When the switching element 2L turns on, the coil 4L, the braking resistor 3L and the switching element 2L
When the capacitance component of the terminal L portion of the piezoelectric body 10 forms a closed circuit and the switching element 2R is turned on in the same manner, the coil
4R, the braking resistor 3R, the switching element 2R, and the electrostatic capacitance component of the terminal R portion of the piezoelectric body 10 form a closed circuit. In this way, when the switching elements 2L, 2R are turned on, a closed circuit is formed, so that the electric energy remaining in the capacitance component of the piezoelectric body 10 is consumed by the braking resistances 3L, 3R of the closed circuit. Will be done. Furthermore,
In this embodiment, the electric energy remaining in the coils 4L, 4R is also consumed by the braking resistors 3L, 3R in the closed circuit.

Therefore, in the first embodiment, the switching elements 2L and 2R are turned on in response to the motor stop signal from the control circuit 6 to form a closed circuit, so that the electric energy remaining in the capacitance component of the piezoelectric body 10 is Immediately consumed, the vibration of the stator 12 is immediately attenuated, the rotation of the rotor 11 is immediately stopped, and the electric energy remaining in the coil is also immediately consumed, so that a better stop characteristic is obtained.

FIG. 2 shows a second embodiment of the present invention. In FIG.
A switching element 7L is connected between the terminal L of the piezoelectric body 10 and the terminal 5L of the oscillator 5, and a braking resistor 3L and a switching element 2L connected in series are connected in parallel to the switching element 7L. Terminal R of body 10 and terminal of oscillator 5
A switching element 7R is connected between 5R, and a braking resistor 3R and a switching element 2R that are connected in series are connected in parallel to the switching element 7R. The control circuit 6 of the ultrasonic motor and the switching elements 7L and 7R are the inverter 8a.
Connected via the control circuit 6 and the switching element
2L and 2R are connected via inverters 8a and 8b connected in series.

Switching elements 7L and 7R when driving the ultrasonic motor
Is on, and the switching elements 2L and 2R are off. At this time, the two-phase alternating current generated from the oscillator 5 is applied to the coil 4L (4R) and the piezoelectric body 10 via the terminal 5L (5R), respectively. When a two-phase alternating current is applied, the piezoelectric body 10 resonates due to the LC resonance circuit formed by the capacitance component of the piezoelectric body 10 and the inductance component of the coil 4L (4R), so that the surface of the elastic body 9 is resonated. A traveling wave is generated to rotate the rotor 11. Further, when the ultrasonic motor is braked, the motor stop signal from the control circuit 6 is input to the oscillator 5 to stop the generation of the two-phase alternating current of the oscillator 5, and the switching elements 7L and 7R are turned off and the switching element 2L is turned on. Turn on 2R. Therefore, the piezoelectric body 10
And coil 4L, braking resistor 3L and switching element 2L
Constitutes a closed circuit, and similarly the piezoelectric body 10, the coil 4R, the braking resistor 3R and the switching element 2R constitute a closed circuit. Similar to the first embodiment, this closed circuit braking resistor 3L
Due to (3R), the electric energy remaining in the electrostatic capacitance component of the coil 4L (4R) and the piezoelectric body 10 is consumed, and the vibration of the starter 12 is immediately attenuated and the rotor 11 stops.

FIG. 3 shows a third embodiment of the present invention. In FIG.
The braking resistor 3L and the switching element 2L connected in series are connected in parallel to the coil 4L, and the braking resistor 3L and the coil 4R are connected.
The switching element 2R is connected between and.

Switching element 2L, 2R when driving ultrasonic motor
Is off and braking resistor 3L is not working. When the motor stop signal is output from the control circuit 6 of the ultrasonic motor, the oscillator 5 stops the output of the two-phase AC and the switching elements 2L and 2R are turned on. Then, like the first and second embodiments described above, the coil 4L (4
R), the braking resistor 3L, the switching element 2L (2R), and the electrostatic capacitance component of the terminal L (R) portion of the piezoelectric body 10 form a closed circuit to form the coil 4L (4R) and the electrostatic capacitance component. The remaining electric energy is consumed by the braking resistance 3L, the vibration of the statuser 12 is immediately attenuated, and the rotor 11 stops.

The present invention is not limited to the three embodiments described above and can be modified as appropriate. In the present embodiment, the coils 4L, 4
It is needless to say that it is not limited to the drive circuit incorporating R, for example, the drive circuit in which the coils 4L and 4R are not incorporated, and in this case, the electric energy remaining in the capacitance component of the piezoelectric body due to the consumption means. Only need to consume. In the first and third embodiments, the coil 4L
(4R), the braking resistance 3L (3R), and the switching element 2L (2R) connected in series have been described as a drive circuit having a configuration in which they are connected in parallel to the electrostatic capacitance component of the piezoelectric body 10, but for example, the coil 4L (4R ) Is the terminal L (R) of the piezoelectric body 10 and the terminal of the oscillator 5.
It is connected in series with 5L (5R) and the coil 4L (4
R) may be a drive circuit having a configuration in which a braking resistor 3L (3R) and a switching element 2L (2R) connected in series are connected in parallel. Furthermore, the braking resistor 3L (3R) and the switching element 2L (2R) connected in series may be replaced with an element having both a resistance component (such as a semiconductor switch) and a switching element such as a transistor.

As described above, according to the present invention, when braking the drive circuit of the ultrasonic motor, the consumption means consumes the electric energy left in the capacitance component of the piezoelectric body of the drive circuit of the ultrasonic motor. By doing so, it is possible to obtain a drive device with good stopping characteristics that can quickly damp the vibration of the elastic body and immediately stop the drive of the rotor.

[Brief description of drawings]

1 is a circuit diagram of an ultrasonic motor driving device according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of an ultrasonic motor driving device according to a second embodiment of the present invention, and FIG. The figure shows a circuit diagram of a drive device for an ultrasonic motor according to a third embodiment of the present invention. FIG. 4 is a circuit diagram of a conventional ultrasonic motor driving device, and FIG. 5 is a perspective view of the ultrasonic motor. (Explanation of symbols of main parts) 5 …… Oscillator 6 …… Control circuit 9 …… Elastic body 10 …… Piezoelectric body 11 …… Rotor 12 …… Stater 2L, 2R, 7L, 7R …… Switching element 3L, 3R… … Braking resistors 4L, 4R… Coil

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliographic references Sho 59-113942 (JP, U)

Claims (2)

[Claims] 1. A first oscillating means for applying a frequency voltage to a first piezoelectric portion fixed to an elastic body to oscillate a first vibration in the first piezoelectric portion; and a first oscillating means fixed to the elastic body. A frequency voltage having a phase different from that of the frequency voltage is applied to the second piezoelectric portion, and a second voltage is applied to the second piezoelectric portion.
A second oscillating means for oscillating the first vibration and a second oscillating means for controlling the operation and non-operation of the first oscillating means and the second oscillating means, and the first vibration and the second vibration. In the drive circuit of the ultrasonic motor that generates the traveling wave in the elastic body and drives the moving body by the traveling wave, the residual wave remains in the first piezoelectric portion arranged along the traveling direction of the traveling wave. Consuming first electric energy, and the second consuming unit arranged along the traveling direction of the traveling wave.
A consuming unit including a second consuming unit that consumes the electric energy remaining in the piezoelectric unit, wherein the control unit respectively deactivates the first oscillating unit and the second oscillating unit. The first consuming unit and the second consuming unit are controlled so that the remaining electric energy is consumed almost at the same time, and the traveling wave generated in the elastic body is rapidly attenuated to brake the moving body. Ultrasonic motor drive circuit characterized by the following. 2. The drive circuit for an ultrasonic motor according to claim 1, wherein the first consuming unit and the second consuming unit consume the remaining electric energy by a common braking resistor.