JPH02285972A - Drive for vibration wave motor - Google Patents

Abstract

PURPOSE:To reduce the weight and to save the space by obtaining driving voltage through switching operation. CONSTITUTION:A drive for a vibration wave motor 7 comprises oscillators 1, 6, a current transformer 2, a smoothing circuit 3, switching circuits 4, 5, and a low voltage power source 8. Switching frequency of switching circuits 4, 5 is set to match with the resonance frequency of the stator of the motor 7. By such arrangement, a group of signals 1B outputted from the smoothing circuit 3 are switched to produce driving signals 1C, 1D to be fed to the motor vibrator.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vibration wave motor drive device, and more particularly to a vibration wave motor drive device that uses ultrasonic waves as a drive source to control the rotational speed of the motor.

[Conventional technology]

First, before explaining a conventional vibration wave motor drive device, the operating principle of a vibration wave motor using traveling waves will be explained.

FIG. 3 is a configuration diagram of a general vibration wave motor.

As shown in FIG. 3, a vibration wave motor 7 that uses a general traveling wave is constructed by bonding a vibrator 20 having the same shape as the resonator 19 to the back surface of a resonator 19 made of an elastic body. This constitutes a stator 23 that is A rotor 24 is similarly provided on the right side of the stator 23, and is pressed with a predetermined pressure by a pressure means such as a disc spring 22. On the surface where the rotor 24 slides against the stator 23,
A lining 21 made of a wear-resistant material, such as a composite plastic material with aromatic polyimide fiber as a filler and a polyurethane resin as a matrix, is provided, and this lining prevents wear with the stator 23. .

-E The vibrator 20 in the vibration wave motor 7 mentioned above uses a piezoelectric element, but this vibrator 20 divides the electrodes into two groups of electrodes, λ/4 (where λ is the stator). 23 wavelength of the natural vibration mode) in the circumferential direction. In this state, when an AC voltage with a temporal phase shifted by π/ (rad) is applied to the two electrode groups,
Flexural vibration occurs in the stator 23 due to the bimetal effect. As a result, two standing waves whose positions and phases are shifted by π/2 (r a d ) are generated in the two sets of electrodes, and these waves are combined on one resonator to form a traveling wave.

FIGS. 4A to 4D are enlarged views of the contact portion between the rotor and the stator, respectively, illustrating the principle of a conventional vibration wave motor using traveling waves.

As shown in FIGS. 4(a) to 4(d), when a signal having a vibration waveform is input to generate progressive deflection vibration in the stator 23, the traveling wave on the stator 23
When focusing on one point E on the surface of , point E draws an elliptical F locus 25.

Since the rotor 24 is in contact with the apex of the traveling wave of the stator 23 and can be moved by friction in the direction of the locus of the apex of the ellipse, the rotor 24 moves in the opposite direction to the traveling direction of the traveling wave, that is, to the left. Therefore, the rotor 24 rotates in a direction opposite to the traveling direction of the traveling wave on the stator 23.

Now, by varying the drive signal input to the vibrator 20 described above, the rotational speed of the vibration wave motor can be controlled. All you have to do is enter.

A method for controlling the rotation speed of such a vibration wave motor is as follows.
As explained in the literature from the Institute of Technology, "Characteristics of Ultrasonic Motors and Servo Control" (published January 22, 1987), the amplitude of a high frequency signal, the frequency of a high frequency signal, the frequency of two or more high frequencies There is a method of changing three types of parameters of signal phase difference.

However, when changing the frequency and phase difference among these three types of parameters, the optimal conditions for driving the vibration wave motor must be intentionally shifted to control the rotation speed. There is a problem that the efficiency of the system decreases.

On the other hand, the method of controlling the amplitude of the high frequency signal allows the rotation speed to be controlled while maintaining the optimum conditions for the vibration wave motor. However, with this amplitude control method, it is difficult to reduce the size and weight of the drive device, as will be explained below.

A conventional vibration wave motor drive device that controls the amplitude of such a high frequency signal will be described below.

FIG. 5 is a block diagram of a vibration wave motor drive device showing an example of such a conventional vibration wave motor drive device.

As shown in FIG. 5, the conventional drive device uses a vibration wave motor 7.
The stator (23 shown in FIG. 3) has an oscillator 1 which generates an oscillatory electrical signal having a frequency such that the stator (23 shown in FIG. 3) is in a resonant state. Since the rotational speed of the vibration wave motor 7 changes depending on the amplitude of the electric signal 30A input to the amplitude control circuit 30, the amplitude control circuit 30 controls the amplitude of the signal generated by the oscillator 1. This high-frequency electrical signal is input to a phase shifter 26, and two or more types of oscillatory signals 26A and 26B having a phase difference of π/2 (RAD) are generated.

generated. Amplifiers 27,28 provide the oscillatory signal 26A.
, 26B, the voltage is amplified and input to the vibrator (20 in FIG. 3) of the vibration wave motor 7. - side, amplifier 27.28
A stabilized high voltage is supplied by a high voltage power supply 29 of about 90 VDC. These two high voltage power supplies are the amplifier 27
．． In order to prevent the power transistor in 28 from becoming saturated and to supply a stable high voltage and current to changes in load, a device consisting of a large-capacity power transformer and power transistor is shown in Figure 6. FIG. 6 is a circuit diagram of the amplifier shown in FIG. 5;

As shown in FIG. 6, the signal voltage VD at the amplifier 27
D and VI are signals supplied from two high voltage power supplies. First, the input signal 34 is amplified by the driver amplifier 33, and further voltage and current amplified by the power transistors 31 and 32 to generate an output signal 35 to be supplied to the vibrator (20 in FIG. 3) of the vibration wave motor 7. Ru. These power transistors 31 and 32 generate heat when driven by the high voltage power supply as described above, and therefore require a large heat sink.

[Problem to be solved by the invention]

The conventional vibration wave motor drive device described above requires a high-voltage DC stabilized power source and a power transistor heatsink for voltage amplification, which has the disadvantage that the drive device is heavy and large in size.

The purpose of the present invention is to reduce the amount of heat dissipated, and
An object of the present invention is to provide a vibration wave motor drive device that realizes weight reduction and space saving.

[Means to solve the problem]

The vibration wave motor drive device of the present invention includes a vibrator that inputs an electric signal and converts it into mechanical vibration, a stator having a resonator coupled to the vibrator, and a rotor that is pressurized and contacts the stator. A vibration wave motor drive device comprising a wave motor and an electric circuit that generates an electric signal having a vibration waveform input to the vibrator of the stator,
a first oscillator whose frequency changes in response to a signal whose voltage continuously changes according to the speed command of the rotor; and a transformer which boosts the voltage of the low voltage power supply in response to the signal from the first oscillator. a voltage smoothing circuit that smoothes the output signal of the transformer; a second oscillator that generates a frequency corresponding to a signal that vibrates the stator of the vibration wave motor; The present invention is characterized in that it includes first and second switching circuits that are controlled by the frequency obtained from the second oscillator and supply a high-frequency oscillating voltage to the vibrator of the oscillating wave motor.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of a vibration wave motor drive device showing one embodiment of the present invention.

As shown in FIG. 1, in this embodiment, an analog signal IA corresponding to the rotational speed is input to an oscillator 1 whose frequency can be controlled using an external signal. The output of the oscillator 1 is boosted by a transformer 2 connected to a low voltage power supply 8 of about several volts, and a smoothing circuit 3 removes high frequency vibration components produced by the oscillator 1. The voltage of the signal group IB smoothed by the smoothing circuit 3 is high when the frequency of the oscillator 1 is high, and low when the frequency is low. Therefore, when the analog signal IA changes, the voltage of the output signal group IB of the smoothing circuit 3 changes accordingly. The signal group IB that has passed through the smoothing circuit 3 is generated by the switching circuits 4 and 5 into drive signal groups IC and ID whose period is the resonance frequency of the vibration wave motor 7. on the other hand,
The oscillator 6 is an oscillator that controls the switching timing of the switching circuits 4 and 5, and the signal generated by this oscillator 6 has a frequency that is four times the resonant frequency of the stator in the vibration wave motor 7, and the resonant frequency is π/4. '
This corresponds to dividing into [RAD]. For this reason,
By inputting adjacent signals among the signals generated by the oscillator 6 to the switching circuits 4 and 5, the vibration wave motor drive signal groups IC and ID whose phase is shifted by π/4 [RAD] with respect to the resonant frequency of the stator are generated. generated. The amplitudes of these drive signal groups IC and ID are determined by the signal group IB after passing through the smoothing circuit 3. Therefore, by changing the analog signal IA, the amplitudes of the drive signal groups IC and ID of the vibration wave motor 7 can be controlled.

However, as explained in FIG. 3 of the conventional example, the vibration wave motor 7 is made by bonding a resonator 19 with a diameter of 30 mm made of an elastic material such as phosphor bronze or aluminum bronze and a vibrator 20 made of a piezoelectric element. The rotor 24 includes a stator 23 and a rotor 24 in which a sliding member 21 is pressed into contact with a disc spring 22. The vibration wave motor 7 is a typical ultrasonic motor that uses traveling waves. In this example, this motor will be explained as the driving target, but this example can be applied to any motor that uses ultrasonic waves as a driving source, such as an ultrasonic motor that uses standing waves generated by other lunge xcA oscillators. An example vibration wave motor drive can be used.

An electric signal (eg, 47 kHz, ultrasonic wave with a Q width of ±30 to 75 V) is input to the vibrator 20 of the stator 23 described above to generate mechanical resonance in the stator 23. In the case of a motor using a traveling wave, by generating a bending traveling wave in the stator 23, a vibration having an elliptical locus F is generated on the stator surface as explained in FIGS. 4(a) to 4(d).

Therefore, the lining 21 is attached to the vibrating stator 23.
When the rotor 24 is brought into contact with pressure by the disc spring 22, the rotor 24
rotational motion occurs.

Now, as explained in FIG. 1, the vibration wave motor drive device of this embodiment includes oscillators 1 and 6, transformer 2, smoothing circuit 3, switching circuits 4 and 5, and low voltage power supply 8. It consists of

This oscillator 1 has a control signal input terminal whose frequency can be controlled in real time by an analog signal IA, and the variable frequency range is 400 [Hz] when the input analog voltage changes from O [V] to 10 [V]. ] to 800 [Hz]. Further, the switching operation is performed with the amplitude between +15 and 0 [■], resulting in a waveform close to a rectangular wave. In response to the output signal from the oscillator 1, the transformer 2 performs a voltage step-up operation, and the waveform after the step-up corresponds to a differentiated rectangular waveform and has a plurality of frequency components.

This boosted signal group becomes a DC electrical signal group IB from which high frequency components are removed by the smoothing circuit 3. The number of windings on the primary and secondary sides of the transformer 2 is set so that the voltage change after passing through the smoothing circuit 3 due to a change in the input analog voltage IA is in the range of 60 [V] to 150 [V]. put. Furthermore, the secondary winding is provided with a center tap terminal,
It is grounded to GND. Because of this, the output signal relative to ground becomes from ±30 [V] to ±75 [V]. This voltage becomes a direct current when the input analog voltage IA is constant. Further, in the switching circuits 4 and 5, the voltage after the output of the smoothing diagram i3 is switched to a positive voltage or a negative voltage by switching transistors. The frequency of this switching is set to match the resonant frequency of the stator of the vibration wave motor 7. Note that switching control is performed by an oscillator 6. The oscillator 6 generates a digital signal having a frequency four times the resonant frequency of the stator. By generating this quadrupled frequency, one wavelength of the oscillator 6 becomes 1/4 wavelength of the resonant frequency of the stator, that is, π/4 [rad]. Therefore, the drive signal for a vibration wave motor using traveling waves is:
π/4 [ra] where the resonance frequency of the stator is the vibration frequency
d] In order to use shifted two-phase signals, two adjacent signals are branched out of the four-cycle signal of the oscillator 6, and two-phase switching with a phase difference of π/4 [rad] with respect to the resonance frequency is performed. Extract the control signal group. This switching control signal causes the signal group IB output from the smoothing circuit 3 to be switched at the resonant frequency, and drive signals IC and ID sent to the vibrator of the vibration wave motor 7 are generated.

FIG. 2 is a specific circuit diagram of the motor drive device shown in FIG. 1.

As shown in FIG. 2, the components constituting the oscillators 1 and 6 of this embodiment are packages of the same size as an 8-16 bin digital TTL IC. Further, in the transformer 2, a high frequency transformer 11 used for a switching power supply and having an outer diameter of about 2 to 3 cm is used. The smoothing circuit 3 includes a bridge diode 12, coils 13 and 14 for removing high frequency noise, and a capacitor 15. moreover,
The switching circuits 4 and 5 are each composed of switching transistors 16 and 17 and their heat sinks, but the switching elements are 1 cm square, and the heat sinks are the same size and about 1 cm thick.

In short, in the above embodiment, when an electric signal corresponding to the drive frequency of a vibration wave motor is obtained by switching operation, the amplitude is controlled by changing the saturation voltage of the switching circuit, and this saturation voltage signal is a low voltage signal. The saturation voltage signal is generated by switching a direct current, and the voltage control of the saturation voltage signal is performed by changing the period of low voltage switching.

〔Effect of the invention〕

As explained above, since the vibration wave motor drive device of the present invention obtains the drive voltage through switching operation, it is possible to reduce the amount of heat dissipated from the power transistors that constitute the switching circuit, and it is also possible to reduce the amount of heat dissipated from the power transistors that constitute the switching circuit. Since it is not necessary, that is, a low voltage source is sufficient, the transformer can be small and lightweight, and there is an effect that the overall weight and space saving can be improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a vibration wave motor drive device showing one embodiment of the present invention, Fig. 2 is a specific circuit diagram of the motor drive device shown in Fig. 1, and Fig. 3 is a general vibration wave motor drive device. 4(a) to 4(d) are enlarged views of the contact portion, respectively, to explain the principle of a conventional vibration wave motor using traveling waves.
FIG. 5 is a block diagram of a conventional vibration wave motor drive device, and FIG. 6 is a circuit diagram of the amplifier shown in FIG. 1.6... Oscillator, 2... Transformer, 3... Smoothing circuit, 4.5... Switching circuit, 7... Vibration wave motor, 8... Low voltage power supply, 9. ]8...Timer, 1
0,1617...Switching transistor (SWT)
r), 11... High frequency transformer, 12... Bridge diode, 13, 1.4... High frequency coil, 15.
... Capacitor, 19... Resonator, 20... Vibrator, 21... Lining, 22 Disc spring, 23... Stator, 24... Rotor.

Claims (1)

[Claims] A vibration wave motor includes a stator having a vibrator that inputs an electric signal and converts it into mechanical vibration, a resonator coupled to the vibrator, and a rotor that is pressed into contact with the stator, and a vibrator of the stator. and an electric circuit that generates an electric signal having an input vibration waveform, the vibration wave motor drive device includes a first vibration wave motor drive device, the frequency of which changes in response to a signal whose voltage changes continuously in accordance with the speed command of the rotor. an oscillator, a transformer that receives a signal from the first oscillator and boosts the voltage of the low voltage power supply, a voltage smoothing circuit that smoothes the output signal of the transformer, and a signal that vibrates the stator of the vibration wave motor. a second oscillator that generates a frequency according to the frequency, and an electric signal obtained from the voltage smoothing circuit is controlled by the frequency obtained from the second oscillator to supply a high-frequency oscillating voltage to the vibrator of the oscillating wave motor. A vibration wave motor drive device comprising a first switching circuit and a second switching circuit.