JP2650952B2 - Drive circuit for vibration type motor - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a driving circuit for a vibration-type motor that frictionally drives a moving body by means of a progressive vibration wave, and in particular, enables ultra-low-speed driving. It relates to a drive circuit.

[Prior Art] A vibration type motor that has recently been put into practical use is disclosed in, for example, JP-A-60-13481, and a low-speed driving method is disclosed in JP-A-60-170473. Have been.

FIG. 5 is a schematic diagram of a vibration type motor.
Reference numerals a and 1b denote piezoelectric elements as well-known electro-mechanical energy conversion elements, which are made of, for example, PZT (zircon lead titanate). Reference numeral 2 denotes a vibrating body made of an elastic material, and adheres the piezoelectric elements 1a and 1b. Reference numeral 3 denotes a moving body, which is pressed against the vibrating body 2 to form a rotor.

The other group of piezoelectric elements 1b is arranged at a pitch shifted from the group of piezoelectric elements 1a of the piezoelectric elements 1a and 1b by a quarter wavelength of the wavelength λ of the vibration wave.

Further, the piezoelectric element 1a is arranged at a half wavelength pitch so that the polarities of adjacent ones are reversed, and the piezoelectric element 1b is similarly formed at a half wavelength pitch.
Adjacent ones are of opposite polarity.

Although not shown, an electrode film is provided on each of the front and back sides of the piezoelectric elements 1a and 1b so that an AC voltage can be applied to each of the piezoelectric elements 1a and 1b.

FIG. 6 is a block diagram of a conventional driving circuit for driving the rotor at a low speed by means of a burst. A driving frequency signal for driving the vibration type motor 10 is output from the oscillator 4. 5 and 6 are phase shifters, and the phase shifter 5 is provided for the piezoelectric element 1a.
A phase shifter for inputting a 90 ° (or 270 °) phase-shifted signal to the piezoelectric element 1b. The phase shifter 6 outputs the output of the phase shifter 5
It is a phase shifter for transferring 180 °. SW is a switch for switching the rotation direction of the rotor 3.

In the prior art shown in FIGS. 5 and 6, the signal output from the oscillator 4 is applied to the piezoelectric element 1a via the modulator 8 → the amplifier 9 and the 90 ° phase shifter 5 outputs 90 °. The phase-shifted signal from the oscillator 4 is supplied to the modulator 8A via the switch SW. Since the intermittent signal as shown in the figure is applied from the synchronous pulse generator 7 to one input terminal of the modulator 8A, the signal from the oscillator 4 through the 90 ° phase shifter 5 is transmitted through the amplifier 9A. It is applied intermittently to the piezoelectric element 1b.

Accordingly, the vibrating body of the vibration type motor 10 (however, FIG. 6 shows only the piezoelectric elements 1a and 1b fixed to the vibrating body 2 and other moving bodies and the like are not shown) is a progressive vibration. The state of generating a wave and the stationary state are repeated in synchronization with the output of the synchronous pulse generator 7.

For this reason, in the vibration type motor 10 of this type, the piezoelectric element
Due to the rising characteristics of 1a and 1b, the stationary state occurs intermittently, and when shifting from this stationary state to the driving state, a large driving force that overcomes the static friction is required, so driving at ultra low speed is not possible It was impossible.

Therefore, the stationary state was abolished, and the driving state by the progressive vibration wave and the driving state by the standing wave, that is, the piezoelectric element 1
The state in which the phase between a and 1b is driven in phase is repeated.
The driving method as shown in the figure was proposed earlier by the present applicant.

[Problems to be Solved by the Invention] However, in the above-described driving method, as shown in FIG. 7, the driving force to the moving body 3 is such that it is repeatedly turned on and off, in other words, However, since the intermittent driving force is applied, the moving body 2 cannot move smoothly, and driving at an extremely low speed is impossible.

The present invention is intended to solve such a problem. That is, in the present invention, the moving body moves smoothly,
It is another object of the present invention to provide a driving circuit for a vibration type motor capable of driving at an extremely low speed.

[Means for Solving the Problems] To achieve the above object, a drive circuit for a vibration type motor according to the present invention converts a frequency signal into first and second drive electric signals.
In a drive circuit of a vibration type motor that obtains a driving force by exciting a vibrating body by applying to a mechanical energy conversion element group, the frequency signal applied to the first driving electro-mechanical energy conversion element group A variable phase shift circuit that repeats increasing and decreasing the phase between a first value and a second value by using the frequency signal shifted by the variable phase shift circuit. It is characterized in that it is applied to a group.

[Operation] According to the present invention, a first output circuit for outputting to a vibration type motor and a frequency signal shifted by a variable phase shift circuit for shifting a phase with respect to the frequency signal are output to the vibration type motor. And a second output circuit that changes the phase shifted by the variable phase shift circuit between a first value and a second value. And it can be driven to a very low speed.

Embodiment FIG. 1 is a block diagram showing an embodiment of a driving circuit for a vibration type motor to which the present invention is applied. In FIG.
11 is an oscillator for generating a high-frequency electric signal, 12 is a synchronous pulse generator, 13 is a variable phase shifter described later, 14 is a 180 ° phase shifter, and 15 and 16 are amplifiers. The mechanical configuration of the vibration type motor is the same as that of the conventional type shown in FIG.
The first output signal via the amplifier 15 is applied to the above-described piezoelectric element 1a, and the second output signal via the amplifier 16 is applied to the piezoelectric element 1b.
Is applied.

FIG. 2 shows an example of a specific circuit of the variable phase shifter 13 of FIG. In FIG. 2, reference numeral 17 denotes a well-known BBD (Bucket Brigad) in which an output signal of the oscillator 11 is input to an input terminal IN thereof.
e Device). 18 is VOC (Voltage Controlled Oscil
lator), that is, a voltage-controlled oscillator that generates an AC signal having a frequency corresponding to the input DC voltage. The output signal of the oscillator 18 is supplied to a clock pulse input terminal of the BBD 17. Reference numeral 19 denotes an LPF (low-pass filter for converting an AC input signal into a DC output signal) to which an output signal from the synchronous pulse generator 12 is supplied to an input terminal.

FIG. 3 is an explanatory diagram of the operation of the variable phase shifter 13 in FIG. 2, and shows the relationship between the phase difference between the piezoelectric elements 1a and 1b and time.

That is, in the driving circuit of the vibration type motor shown in FIG. 1, the oscillator 11 generates a sine wave signal having a frequency substantially equal to the resonance frequency of the vibration type motor,
After being amplified at 15, it is applied as a first output signal to the piezoelectric element 1a forming the A phase.

The variable phase shifter 13 adjusts the phase of the output of the oscillator 11 to a certain range (3
In the figure, it is continuously shifted over the range of 10 ゜ to 30 ゜),
The phase-shifted signal is amplified by the amplifier 16 and then applied as a second output signal to the piezoelectric element 1b forming the B phase.

FIG. 4 shows the relationship between the speed and the time of the vibration type motor when the phase is swept over the range of 10 ° to 30 °. However, the sweep range is not limited to the above range, and may be appropriately selected.

In FIG. 1, when the switch SW is switched to the 180 ° phase shifter 14, the phase-shifted signal from the variable phase shifter 13 is shifted by 180 ° Since the second output signal is applied as the second output signal to the piezoelectric element 1b forming the B phase, the vibration type motor is driven in the reverse direction.

[Effects of the Invention] As described above, according to the present invention, the first output circuit that outputs to the vibration type motor and the frequency signal that is shifted by the variable phase shift circuit that shifts the phase with respect to the frequency signal And a second output circuit for outputting to the vibration type motor, the phase shifted by the variable phase shift circuit
It is possible to drive the vibration type motor to a very low speed without the influence of the static friction force by repeatedly increasing and decreasing the value between and the second value.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing one embodiment of a drive circuit of the present invention,
FIG. 2 is an explanatory diagram showing an example of a specific circuit of the variable phase shifter of FIG. 1, FIG. 3 is an explanatory diagram of the operation of the circuit of FIG.
FIG. 5 is an explanatory view showing the relationship between speed and time of a vibration type motor driven by the drive circuit of FIG. 1, FIG. 5 is a perspective view schematically showing a mechanical configuration of a conventional vibration type motor, and FIG. FIG. 1 is an explanatory view showing an example of a conventional drive circuit of this type, and FIG.
FIG. 7 is an explanatory diagram showing the relationship between the speed and the phase difference of the vibration type motor driven by the drive circuit of FIG. 6 and time. 1a, 1b: Piezoelectric element, 2: Vibrating body 3: Moving body, 11: Oscillator 12, Synchronous pulse generator 13: Variable phase shifter, 14: 180 ° phase shifter 15, 16 … Amplifier, 17 …… BBD 18 …… VCO, 19 …… LPF

Claims (1)

(57) [Claims] 1. A driving circuit for a vibration-type motor that obtains a driving force by exciting a vibrating body by applying a frequency signal to a first and a second group of driving electro-mechanical energy conversion elements. A variable phase shift circuit is provided which repeats increasing and decreasing the phase between first and second values for the frequency signal applied to the driving electro-mechanical energy conversion element group. A driving circuit for a vibration-type motor, wherein the phased frequency signal is applied to the second driving electro-mechanical energy conversion element group.