JPH01107681A - Driver circuit for oscillatory wave motor - Google Patents

Abstract

PURPOSE:To improve drive efficiency by connecting a resonance element constituting a resonance circuit to a transformer and driving a motor by the secondary-side output of the resonance element. CONSTITUTION:A driver circuit for an oscillatory wave motor 43 is composed of an oscillator 2 generating high frequency for drive, a phase shifter 3 in phase difference at 90 deg., a rotation changer 4, buffers 5-12, transistors(Tr) 21-28 for switching, diodes 29-36 for protecting the Trs, capacitors 37-38 for resonance with the inductance of a transformer primary-side winding, transformers 39-40, and coils 41-42 for shaping a waveform. The resonance frequency of the transformer using resonance on the primary side and resonance frequency peculiar to the motor are conformed while resonance frequency and the Q of a resonance circuit are set so that the characteristics of frequency-output voltage at the time of displacement from a resonance point coincide with characteristics at a point where the input currents of the oscillatory wave motor 43 are minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a drive circuit for a vibration wave motor.

[Conventional technology]

Conventionally, when controlling the rotation speed of a vibration wave motor, the rotation speed is controlled by applying a constant voltage to the vibration wave motor and changing the driving frequency, as shown in Figure 4, or by controlling the rotation speed of the vibration wave motor. The rotational speed is controlled by changing the applied voltage, or by a combination of these, the rotational speed is controlled by switching several voltages and controlling by changing the frequency.

[Problem to be solved by the invention] However, in the conventional rotation speed switching method described above, by keeping the voltage applied to the vibration wave motor constant (for example, 30 V) and changing the driving frequency as shown in Fig. 4, When controlling the rotation speed (by changing the 30V line in Figure 4), the 30V in Figure 3
The resonance frequency f when the driving voltage is 30V, as in the case of Nouin. However, when the rotational speed decreases, the current flowing through the vibration wave motor increases, which deteriorates the driving efficiency of the motor.

Furthermore, if a large number of voltage sources are switched as shown at 30V, 25V, and 20V in FIG. 4 and controlled in accordance with changes in frequency, speed control becomes possible using voltages and frequency bands with relatively good drive efficiency.

For example, in the state of 30V, the frequency is changed in the range a in Fig. 4, the rotation speed is controlled in the range N, -N2, and N2 to N2.
In the range of 2, the driving voltage is switched to 25V, and the resonant frequency f2. If you change the frequency only in the range from to b, then switch the drive voltage to 20V in the range of N and ~N4 and change the frequency in the range from f2° to C, the resonance frequency under 20V, you can control the rotation speed in a wide range. This can be achieved by changing the frequency without significantly deviating from the resonance frequency, and it is possible to prevent deterioration of drive efficiency.

However, this method has the problem of requiring multiple voltage sources.

[Means to solve the problem]

The present invention provides a transformer with a resonant circuit for the primary coil.
By connecting resonant elements such as condensers, and applying a frequency signal to the primary side of the transformer, a secondary side output of the transformer is generated, and this output drives the motor. The present invention aims to provide a drive circuit for a vibration wave motor that solves the above problem by automatically changing the frequency and output voltage of the secondary side output to a combination state with good motor drive efficiency by changing the frequency of the frequency signal. It is something to do.

〔Example〕

FIG. 1 shows an embodiment of the vibration wave motor drive circuit according to the present invention, in which 1 is a battery as a power source, 2 is an oscillator that generates high frequency waves for driving the vibration wave motor, and the oscillator is has variable means for manually varying the output frequency. 3 sets the phase of the oscillator output to 90'
A phase shifter for shifting and creating a driving high frequency wave with a phase difference of 90'', 4 a rotation direction switching device for changing the phase of the driving high frequency wave in order to change the rotation direction of the vibration wave motor, 5. 6.9.10 is a non-inverting buffer for driving the switching transistor described later, 7, 8, 11
．． 12 is an inversion buffer for driving the switching transistor by inverting the phase of the driving high frequency; 13;
20 is the base resistance of the transistor, 21 to 28 are switching transistors, 29 to 36 are protection diodes to protect the transistor by absorbing the back electromotive force of the transformer, and 37.38 is the primary side of the transformer. The inductance of the winding and the resonance capacitor for series resonance, 39.40 is a transformer that boosts the low voltage driving high frequency to the voltage required to drive the vibration wave motor, 41.42 is a A waveform shaping coil 43 is used to convert the boosted driving high frequency into a sine wave, and 43 is a vibration wave motor driven by high voltage and high frequency.

FIG. 6 is a sectional view of the vibration wave motor 43 viewed from the circumferential direction, in which 43-1 is a rotor, 43-2 is a vibrator, 4
3-4 is a polarized piezoelectric element (electrostrictive element) attached to the vibrating body 43-2, and 43a and 43b are electrodes. The vibrating body 43-'2 and the piezoelectric body 43-4 constitute a stator, and the rotor 43-1 is in frictional contact with the vibrating body 43-2.

Among the electrodes 43a and 43b, if the wavelength of the bending traveling wave in the vibrating body 43-2 is λ, 43a is a driving electrode and
They are arranged on the piezoelectric body 43-4 at intervals of 2, and 43b is a driving electrode, which is also arranged on the piezoelectric body 43-4 at intervals of λ/2.

Further, the electrodes 43a and 43b are out of phase in position by 3λ/4, and the piezoelectric material to which the driving voltage is applied to the electrode 43a constitutes an A-phase piezoelectric material, and the driving voltage is applied to the electrode 43b. The B-phase piezoelectric body is composed of the piezoelectric bodies. Since the polarization process of these piezoelectric bodies and the electrode arrangement itself are well known, detailed explanation thereof will be omitted.

In the above configuration, by applying frequency voltages having a phase difference of 906 to the electrode 43a and the electrode 43b, the vibrating body 4
A progressive vibration wave is generated on the rotor 43-2, and the rotor 43-1
is driven by the vibration wave.

Next, the operation of the above configuration will be explained. The high frequency pulse generated by the oscillator 2 is shifted by 90° by the 90' phase shifter 3,
Creates a high frequency wave with the same frequency and a phase difference of 90° for driving a vibration wave motor. Next, use the rotation direction switch 4 to adjust the phase difference to 90
°The rotation direction of the vibration wave motor is determined by whether it is delayed or advanced.

The signals for driving the vibration wave motor thus generated are supplied to the bases of the switching transistors through buffers 5 to 12, respectively, and become switching signals. Now, assuming that the output pulse of the oscillator 2 is as shown in FIG. 2(a), the transistor 21 performs an on/off operation as shown in FIG. 2(d), while the transistor 22 performs an on/off operation as shown in FIG. 2(b). perform an action. The output of the oscillator 2 via the inverter 7.8 is as shown in FIG. 2(C), the transistor 23 operates on and off as shown in FIG. 2(b), and the transistor 24 operates as shown in FIG.
) performs on/off operations. Therefore, current flows alternately in different directions in the primary coil of the transformer 39, and a high voltage and high frequency voltage is generated in the secondary coil of the transformer 39.

On the other hand, the output of the rotation direction switch 4 is the pulse shown in FIG.
It turns on and off as shown in figure (f), and the transistor 25.28
performs on/off operations as shown in FIG. 2(g). For this reason,
Current also flows alternately in different directions in the primary coil of the transformer 40, and a high-voltage, high-frequency voltage is also generated as an output of the secondary coil of the transformer 40.

As mentioned above, since the output pulses of the oscillator 2 and the rotation direction switch 4 have a 90° phase difference, the transformer 39.
The output of 0 also has a 90° phase difference, and the coil 41
．． 42, each electrode 43a, 43 is shaped into a sine wave.
b.

As a result, high-voltage, high-frequency voltages having a phase difference of 90" are applied to the A-phase and B-phase piezoelectric bodies, and as described above, the vibration wave motor 4
3 rotates.

Resonant capacitors 37 and 38 are connected in series to the primary coil of the transformer 39 or 40 to form a series resonant circuit.

In the series resonant circuit, the highest voltage is applied to the primary coil of the transformer near the resonant frequency of the circuit, and as the voltage deviates from the resonant frequency, the voltage applied to the primary coil decreases. Therefore, the output voltage on the secondary side of the transformer is highest when it is near the resonant frequency of the primary side resonant circuit, as shown in FIG. 5, and the output voltage decreases as it deviates from the resonant frequency.

Here, the frequency-current relationship of the vibration wave motor is as shown in Figure 3, and the frequency-rotation speed relationship is as shown in Figure 4. When the rotation speed is changed, the input current becomes thicker as it deviates from the resonant frequency, and the drive efficiency of the motor deteriorates.

Therefore, in order to prevent the drive efficiency from deteriorating, if you change the drive voltage along with the frequency and always drive the motor at a point where the input current is small, each time the rotation speed changes without deteriorating the motor drive efficiency. can.

Therefore, in the present invention, the resonant frequency of a transformer that uses resonance on the negative side matches the resonant frequency specific to the vibration wave motor, and the frequency-output voltage characteristic when the vibration wave motor deviates from the resonance point is determined by the vibration wave motor. The resonant frequency and the Q of the resonant circuit are set so as to match the frequency-voltage characteristics at the point where the input current - is minimum. With this, when the frequency is changed, the voltage applied to the vibration wave motor changes, and the current is always controlled to the minimum, improving drive efficiency.

That is, it is assumed that the oscillation frequency of the oscillator 2 is now set to the resonant frequency f so of the series resonant circuit, and at this time, 30V is generated as the secondary output of the transformer 39,40. As mentioned above, since the resonant frequency of the vibration wave motor and the resonant frequency of the series resonant circuit match, the motor operates at a high driving efficiency as shown by the 30V line in FIG. 3 at this time.

From this state, when the output frequency of the oscillator 2 is changed from f3° to f2B in order to lower the rotational speed of the motor, the secondary output of the transformer becomes 25V as shown in FIG. In this state, as shown in Figure 3 (the resonance frequency of the motor is 25V), the motor operates with high driving efficiency.

Moreover, in order to further reduce the rotation speed, if the output frequency of oscillator 2 is changed and shifted from f211 to f2°, the fifth
As shown in the figure, the secondary output of the transformer becomes 20V, and even in this state, as shown in Figure 3 (the resonance frequency of the motor under 20V), the motor operates with high drive efficiency in state 2 and 1. ing.

As described above, in the present invention, when the drive frequency is changed when controlling the rotational speed of the motor, the drive voltage also changes automatically, and the relationship between the motor drive voltage and the drive frequency always minimizes the input current of the motor. It is controlled so that it becomes.

〔effect〕

As described above, in the present invention, when the drive frequency is changed, the drive voltage is automatically changed, and the combination of frequency and drive voltage that always maintains the motor in a resonant state is maintained. Efficiency can be greatly improved, and since the structure requires only a single driving voltage source, the above object can be achieved without complicating the structure.

In the embodiment, a pulse for directly determining the driving frequency is obtained from the oscillator 2, but a frequency dividing circuit for frequency dividing the oscillator output may be provided, and the driving frequency may be determined by the output of the frequency dividing circuit. In this case, the drive frequency is made variable by selecting the frequency dividing stage. Furthermore, although a piezoelectric body is used as the motor in this embodiment, an electrostrictive element may also be used. Further, as a specific element, YZT or the like can be used.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the vibration wave motor drive circuit according to the present invention, FIGS. 2(a) to 2(g) are waveform diagrams for explaining the circuit operation of the first interlude, and FIG. 4 are explanatory diagrams showing the drive characteristics of the vibration wave motor, FIG. 5 is an explanatory diagram showing the characteristics of the transformer of the embodiment shown in FIG. 1, and FIG. 6 is a sectional view showing the configuration of the vibration wave motor. be. 37.38...Condenser 39.40...Transformer 43...Vibration wave motor Fig. 3 11 turbidity IL dormitory 6 flash + run-in

Claims (1)

[Claims] A progressive vibration wave is formed in the vibrating body by applying frequency voltages with different phases to a piezoelectric body or an electrostrictive element arranged with a phase difference with respect to the vibrating body, and In a drive circuit for a vibration wave motor that drives a moving object in The frequency voltage is supplied to the piezoelectric body or the electrostrictive element at the secondary coil output of the transformer, and the vibration wave motor is controlled at the frequency and voltage at the output voltage of the secondary coil. and adjusting means for adjusting the frequency of the drive signal from the drive signal application circuit,
A drive circuit for a vibration wave motor, characterized in that the frequency and voltage value of the output voltage of the secondary coil are changed.