JPH0516277B2 - - Google Patents

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]

When controlling the rotation speed of conventional vibration wave motors,
As shown in Figure 4, the number of rotations is controlled by applying a constant voltage to the vibration wave motor and changing the driving frequency, or the number of rotations is controlled by changing the voltage applied to the frequency motor. Or a combination of these is used to control the rotational speed using several voltage switches and frequency changes.

[Problem that the invention is trying to solve]

However, in the conventional rotation speed switching method described above, by keeping the voltage applied to the vibration wave motor constant (for example, 30) and changing the driving frequency as shown in Figure 4 (changes on the line 30 in Figure 4). )
When the number of times is controlled, the resonance frequency f ₃₀ when the driving voltage is 30, as shown in the line 30 in Figure 3.
However, when the rotational speed decreases, the current flowing through the vibration wave motor increases, resulting in a deterioration of the driving efficiency of the motor. Also, 30 in Figure 4
, 25 and 20, if a large number of voltage sources are switched and controlled in accordance with changes in frequency, speed control becomes possible using a voltage and frequency band with relatively good drive efficiency.

For example, in the state of 30, the frequency is changed in the range a in Figure 4 and the rotation speed is controlled in the range of N ₁ to N ₂ , and in the range of N ₂ to _{N 2} , the drive voltage is switched to 25, and the rotation speed is changed to 25. _The resonant frequency _{f at}
By changing the frequency in the range from f ₂₀ to c, a wide range of rotational speeds can be realized by changing the frequency without significantly deviating from the resonant frequency, and deterioration of drive efficiency can be prevented.

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

[Means to solve the problem]

The present invention connects a resonant element such as a capacitor that forms a resonant circuit to a primary coil of a transformer, and generates a secondary output of the transformer by applying a frequency signal to the primary side of the transformer. By driving the motor with the output and changing the frequency of the frequency signal to the primary side, the frequency and output voltage of the secondary side output can be automatically changed to a combination state with good motor drive efficiency, and the above problem can be solved. The present invention aims to provide a drive circuit for a vibration wave motor that eliminates the problem.

〔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 shifts the phase of the oscillator output by 90°,
A phase shifter to create a driving high frequency with a phase difference of 90°,
4 is to change the rotation direction of the vibration wave motor.
A rotation direction switch for changing the phase of the driving high frequency wave; 5, 6, 9, and 10 are non-inverting buffers for driving switching transistors to be described later; 7, 8, 11, and 12 are the phases of the driving high frequency wave. 13 to 20 are base resistances of the transistors, 21 to 28 are switching transistors, and 29 to 36 absorb the back electromotive force of the transformer to drive the transistors. Protection diodes 37 and 38 are used to connect the inductance of the primary winding of the transformer to resonance capacitors for series resonance. 39 and 40 are used to connect the low voltage drive high frequency to drive the vibration wave motor. Transformer to step up the voltage to the required voltage, 41,4
2 is a waveform shaping coil for converting 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, and 43-1 in FIG. 6 is a rotor;
2 is a vibrating body; 43-4 is a polarized piezoelectric body (electrostrictive element) attached to the vibrating body 43-2;
3a 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 arranged on the piezoelectric body 43-4 at an interval of λ/2, and 43b is a driving electrode. electrode, the electrode is also λ/2
They are arranged on the piezoelectric body 43-4 at intervals. Also, electrode 43
A and 43b are out of phase in position by 3λ/4, and constitute an A-phase piezoelectric body with a piezoelectric body to which a driving voltage is applied at electrode 43a, and a driving voltage is applied at electrode 43b. A B-phase piezoelectric body is constituted by the piezoelectric body. 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, the electrode 43a and the electrode 43b
By applying a frequency voltage with a phase difference of 90° to
Progressive vibration waves are generated on the vibrating body 43-2, and the rotor 43-1 is driven by the vibration waves.

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 to create a high-frequency wave with the same frequency but a 90° phase difference for driving the vibration wave motor. Next, the rotation direction changer 4 determines the rotation direction of the vibration wave motor depending on whether the phase difference is delayed or advanced by 90 degrees.

The vibration wave motor drive signals created in this way are passed through buffers 5 to 12, respectively.
Supplied to the base of the switching transistor,
Serves as a switching signal. Now, assuming that the output pulse of the oscillator 2 is as shown in FIG. 2a, the transistor 21 performs an on/off operation as shown in FIG. 2d, while the transistor 22 performs an on/off operation as shown in FIG. 2b. The output of the oscillator 2 via the inverters 7 and 8 is as shown in FIG. 2c, the transistor 23 turns on and off as shown in FIG. 2b, and the transistor 24 turns on and off as shown in FIG. 2d. . Therefore, current flows in the primary coil of the transformer 39 in different directions alternately, 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.
The transistors 6 and 27 are turned on and off as shown in FIG. 2f, and the transistors 25 and 28 are turned on and off as shown in FIG. 2g. Therefore, current flows alternately in the primary coil of the transformer 40 in different directions, causing the transformer 40 to
A high-voltage, high-frequency voltage is also generated as the output of the zero secondary coil.

As mentioned above, since the output pulses of the oscillator 2 and the rotational direction switch 4 have a 90° phase difference, the outputs of the transformers 39 and 40 also have a 90° phase difference, and the coils 41 and 42 convert them into sine waves. After being shaped, it is applied to each electrode 43a, 43b. 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 the vibration wave motor 43 rotates as described above.

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 frequency 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-rotational speed relationship is as shown in Figure 4. At a constant voltage (for example, 30),
When changing the rotation speed by changing the frequency, the input current increases as it deviates from the resonant frequency.
Motor drive efficiency deteriorates. Therefore,
In order to prevent the drive efficiency from deteriorating, if the drive voltage is changed along with the frequency and the motor is always driven at a point where the input current is small, the rotation speed can be changed without deteriorating the motor drive efficiency.

Therefore, in the present invention, the resonant frequency of a transformer that uses resonance on the primary side is matched with 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 The resonant frequency and Q of the resonant circuit are set 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, controlling the current so that it is always at a minimum, improving drive efficiency.

That is, the oscillation frequency of the oscillator 2 is now set to the resonant frequency f ₃₀ of the series resonant circuit, and at this time,
It is assumed that 30 is generated as the secondary output of the transformers 39 and 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 with high driving efficiency as shown by line 30 in FIG. 3 at this time. From this state, in order to reduce the rotational speed of the motor, the output frequency of the oscillator 2 is changed and shifted from _f30 to _f25 , and the secondary output of the transformer becomes 25 as shown in FIG.
In this state, the resonance frequency of the motor is below 25 as shown in Figure 3, so it operates with high drive efficiency. In addition, in order to further reduce the rotation speed, if the output frequency of oscillator 2 is changed and shifted from f ₂₅ to f ₂₀ , the secondary output of the transformer becomes 20 as shown in Figure 5.
Even in this state, the resonant frequency of the motor is below 20 as shown in Figure 3, and even in this state, the motor is operating with high drive efficiency.

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

〔effect〕

As described above, in the present invention, when the drive frequency is changed, the drive voltage also changes automatically, 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 drawings]

FIG. 1 is a circuit diagram showing an embodiment of a drive circuit for a vibration wave motor according to the present invention, and FIGS.
A waveform diagram for explaining the circuit operation shown in Fig. 3,
4 is an explanatory diagram showing the driving 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. 37, 38... Capacitor, 39, 40... Transformer, 43... Vibration wave motor.

Claims (1)

[Claims] 1. The conversion element 4 having an electro-mechanical energy conversion element 43 that generates driving vibration, an AC signal generation circuit 2, and output voltage variable circuits 37 to 42.
3, the vibration motor uses the vibration generated in the generator circuit 2 as a driving source, and the alternating current signal generating circuit 2 is capable of varying the frequency of the output alternating current signal, and the output voltage variable circuits 37 to 42 are connected to the generating circuit 2. It includes means 37 and 38 for changing the voltage level of the AC signal in response to a change in the frequency of the AC signal output from the conversion element 43. contact body 43-1 which is supplied to the contact body 43-1 and is thereby driven by the vibration.
A vibration motor characterized in that the relative speed between the converter element and the converter element can be changed.