JP2002017094A - Ultrasonic motor drive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ultrasonic motor drive that is of small size and allows omission of a phase shifter. SOLUTION: The ultrasonic motor drive 51 is generally provided with an oscillator 2 and two piezoelectric transformers 3 and 52. The piezoelectric transformers 3 and 52 comprise a piezoelectric unit, respectively and include a primary-side driving portion and a secondary-side generating portion. The AC output voltages of the piezoelectric transformers 3 and 52 are different in phase from each other substantially by 90 deg. and used as driving voltage for driving a traveling wave ultrasonic motor 43.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic motor driving device.

[0002]

2. Description of the Related Art Generally, a traveling-wave type ultrasonic motor applies a driving AC voltage having a phase difference of 90 degrees to electrodes of a stator on which a piezoelectric element is mounted, as described in JP-A-3-112378. There is a need to. Also, the input impedance of the piezoelectric element mounted on the stator is relatively high, and a drive circuit for supplying a drive AC voltage to the stator requires one winding transformer for each drive AC voltage having a different phase.

[0003]

As described above, the driving device of the conventional traveling wave type ultrasonic motor requires a winding transformer for each driving AC voltage having a different phase, and the winding transformer is usually large in size. Therefore, it was difficult to reduce the size of the device. In addition, a driving device for a traveling-wave ultrasonic motor always requires a phase shifter, which has led to complication of a circuit and an increase in cost.

Accordingly, an object of the present invention is to provide a small-sized and
An object of the present invention is to provide an ultrasonic motor driving device capable of omitting a phase shifter.

[0005]

In order to achieve the above object, an ultrasonic motor driving apparatus according to the present invention comprises an oscillator and one piezoelectric transformer, and the AC voltage from the oscillator is applied to one piezoelectric transformer. Is input to generate a drive voltage for driving the linear type ultrasonic motor.

[0006] With the above configuration, since the piezoelectric transformer is used, the size of the device can be reduced.

Further, an ultrasonic motor driving device according to the present invention includes an oscillator, a first piezoelectric transformer, and a second piezoelectric transformer, and receives a primary voltage by inputting an AC voltage from the oscillator to the first piezoelectric transformer. A first driving voltage of a traveling wave type ultrasonic motor is generated by causing a piezoelectric transverse effect or a piezoelectric longitudinal effect in a side driving unit and a piezoelectric longitudinal effect or a piezoelectric transverse effect in a secondary side power generating unit. And the second
By inputting an AC voltage from an oscillator to the piezoelectric transformer, a piezoelectric effect in the same direction as that of the primary drive unit of the first piezoelectric transformer is generated in the primary drive unit, and A piezoelectric effect is generated in a direction different from that of the secondary-side power generation unit of the first piezoelectric transformer to generate a second drive voltage of the traveling wave type ultrasonic motor, and the first drive voltage and the second drive voltage Has a phase difference of about 90 degrees.
Thereby, it is not necessary to use a phase shifter.

Further, an ultrasonic motor driving device according to the present invention includes an oscillator and one piezoelectric transformer, and the piezoelectric transformer has at least one input terminal and at least two output terminals, and the input terminal receives the signal from the oscillator. , The first drive voltage and the second drive voltage of the traveling wave type ultrasonic motor are output from at least two output terminals, respectively, and the first drive voltage and the second drive voltage are output. Has a phase difference of about 90 degrees.

Alternatively, an ultrasonic motor driving device according to the present invention includes an oscillator and one piezoelectric transformer, and the piezoelectric transformer has at least one primary driving unit and at least two secondary power generating units, A piezoelectric transverse effect or a piezoelectric longitudinal effect is generated by inputting an AC voltage from an oscillator to the side driving unit, and a piezoelectric longitudinal effect is generated in at least one secondary-side power generating unit, and the second wave of the traveling wave type ultrasonic motor is generated. And generating a second driving voltage for the traveling wave type ultrasonic motor by generating a piezoelectric transverse effect in another at least one secondary-side power generation unit. The phase difference of the second drive voltage is substantially 90 degrees. Thereby, two or more AC output voltages whose phases are different from each other by approximately 90 degrees can be supplied by one piezoelectric transformer, and the size of the device is further reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an ultrasonic motor driving device according to the present invention will be described below with reference to the accompanying drawings. In the following embodiments, the same components and the same portions are denoted by the same reference numerals, and duplicate description will be omitted.

[First Embodiment, FIGS. 1 to 5] FIGS. 1 and 2 show an example of an ultrasonic motor driving apparatus according to the present invention. The ultrasonic motor driving device 1 generally includes an oscillator 2 and a piezoelectric transformer 3.

The piezoelectric transformer 3 is composed of a piezoelectric unit 11 and includes a primary drive unit 12 and a secondary power generation unit 13. As shown in FIGS. 3 to 5, the piezoelectric transformer 3 is a Rosen type piezoelectric transformer, and a ceramic green sheet such as lead zirconate titanate (PZT) is manufactured by a doctor blade method. The hot-side internal electrode 21 and the ground-side internal electrode 22 are respectively formed by using a method such as a screen printing method, and these green sheets are laminated and pressed, cut into a square shape, and then sintered, and P1, P2 ( The piezoelectric unit 11 is polarized in the thickness direction of the piezoelectric transformer 3) and P3 (longitudinal direction of the piezoelectric transformer 3).

The piezoelectric unit 11 has an input external electrode 1
4. A ground external electrode 15 and an output external electrode 16 are formed. These external electrodes 14 to 16 are formed by a technique such as silver baking. The input external electrode 14 is electrically connected to the hot-side internal electrode 21 and is connected to the ground external electrode 1.
5 is electrically connected to the ground side internal electrode 22. The length of the piezoelectric transformer 3 is 30 mm, the width is 6 mm, and the thickness is 1.4 mm (representative value).

The oscillator 2 outputs an AC voltage having the same frequency as the longitudinal natural resonance frequency of the piezoelectric body unit 11. The AC voltage from the oscillator 2 is input to the piezoelectric transformer 3 via the amplifier 4. When an AC voltage is applied to the piezoelectric transformer 3 between the input external electrode 14 and the ground external electrode 15, the piezoelectric unit 11 vibrates in the longitudinal direction in a primary vibration mode. Thereby, the secondary side power generation unit 13
Then, electric charges are generated by the piezoelectric effect, and the output external electrodes 16
And a grounded external electrode 15 to generate a boosted AC output voltage. The AC output voltage of the piezoelectric transformer 3 is used as a drive voltage for driving the ultrasonic motor 5.

As shown in FIG. 2, the ultrasonic motor 5 according to the first embodiment has two Langevin vibrators 30,
This is a linear ultrasonic motor in which 31 is attached to both right and left ends of a rail 32. When an AC output voltage from the piezoelectric transformer 3 is applied to one of the Langevin vibrators 30, the tip 30a of the Langevin vibrator 30 is
2 reciprocates in the axial direction, and a traveling wave traveling in the direction indicated by arrow K1 in FIG. Therefore, the slider 33 mounted on the rail 32 moves in the traveling direction of the traveling wave (the direction indicated by the arrow K1).

When the switch S is switched to apply an AC output voltage from the piezoelectric transformer 3 to the other Langevin vibrator 31, the tip 31a of the Langevin vibrator 31 reciprocates in the axial direction of the vibrator 31 and the rail 32 Arrow K on
A traveling wave traveling in the direction indicated by 2 is generated. Therefore, the slider 33 moves in the traveling direction of the traveling wave (the direction indicated by arrow K2).
Go to

The ultrasonic motor driving apparatus 1 having the above-described configuration can be reduced in size because the piezoelectric transformer 3 is used, and can reduce radiation of noise due to magnetic flux generated in a conventional winding transformer.

[Second Embodiment, FIGS. 6 to 16] FIG. 6 shows another example of the ultrasonic motor driving device according to the present invention. The ultrasonic motor driving device 51 generally includes an oscillator 2 and two piezoelectric transformers 3 and 52. An AC voltage from the oscillator 2 is directly input to the piezoelectric transformers 3 and 52. The piezoelectric transformer 3 is the same as that described in the first embodiment, and a detailed description thereof will be omitted (see FIGS. 3 to 5).

On the other hand, as shown in FIG. 7 and FIG. 8, the piezoelectric transformer 52 forms a hot side internal electrode 61a and a ground side internal electrode 62a of the primary side driving section 53 on a ceramic green sheet, respectively. The hot-side internal electrode 61b and the ground-side internal electrode 62b of the secondary-side power generation unit 54 are formed, and these green sheets are laminated and pressed, cut into a square shape, sintered, and polarized in the directions of P1 and P2. A piezoelectric unit 59 is provided. A gap of about 0.2 to 0.5 mm is secured between the internal electrodes 61a and 62a of the primary drive section 53 and the internal electrodes 61b and 62b of the secondary power generation section 54 to prevent a short circuit. I have.

The piezoelectric unit 59 has an input external electrode 5
5, an output external electrode 57, an input-side ground external electrode 56, and an output-side ground external electrode 58 are formed. The input external electrode 55 is electrically connected to the hot-side internal electrode 61a, and the input-side ground external electrode 56 is electrically connected to the ground-side internal electrode 62a. Output external electrode 5
7 is electrically connected to the hot-side internal electrode 61b, and the output-side ground external electrode 58 is electrically connected to the ground-side internal electrode 62b.

When an AC voltage is applied to the piezoelectric transformer 52 between the input external electrode 55 and the input-side ground electrode 56, the primary-side driving section 53 excites vibration by a piezoelectric transverse effect. Thus, the secondary-side power generation unit 54 converts the vibration into electricity by the lateral piezoelectric effect, and generates a boosted AC output voltage between the output external electrode 57 and the output-side ground electrode 58. That is, the piezoelectric transformer 52 is
The secondary power generation unit 54 and the secondary power generation unit 54 both utilize the piezoelectric lateral effect. On the other hand, in the piezoelectric transformer 3, the primary side drive unit 12 utilizes the piezoelectric lateral effect, while the secondary side power generation unit 13 utilizes the piezoelectric longitudinal effect.

FIGS. 9 and 10 show that the width of the piezoelectric transformer 3 is 6 mm, the thickness is 1.4 mm, the length L1 of the drive unit 12 is 18 mm, the length L2 of the power generation unit 13 is 12 mm, and the drive unit 1
2 is a graph showing a ratio (hereinafter referred to as a step-up ratio) and a phase of an input voltage to an output voltage when the number of internal electrodes is eight and the value of the load resistance is variously changed. 11 and 12 show that the width of the piezoelectric transformer 52 is 6 mm, the thickness is 1.4 mm, the length L1 of the driving unit 53 is 19.5 mm, the length L2 of the power generation unit 54 is 12 mm, and Power generation unit 5
4 is a graph showing the boost ratio and the phase when the number of stacked internal electrodes is 8 and the value of the load resistance is variously changed. As can be seen from FIGS.
In both the piezoelectric transformer 52 and the piezoelectric transformer 52, the step-up ratio characteristic and the phase characteristic change with the change in the value of the load resistance.

FIG. 13 is a graph showing the boost ratio when the load resistance is 2 kΩ. The solid line indicates the boost ratio of the piezoelectric transformer 3 and the dotted line indicates the boost ratio of the piezoelectric transformer 52. FIG. 14 is a graph showing the phase of the output voltage with respect to the input voltage. The solid line indicates the piezoelectric transformer 3 and the dotted line indicates the piezoelectric transformer 52. In FIG. 14, the phase difference between the output voltage of the piezoelectric transformer 3 and the output voltage of the piezoelectric transformer 52 is also indicated by a dashed line. As can be seen from FIGS. 13 and 14, the output voltage of the piezoelectric transformers 3 and 52 has a phase difference of about 90 degrees near the resonance frequency (around 53 kHz) where the step-up ratio of the piezoelectric transformers 3 and 52 is maximum. . Thus, a boosted AC output voltage having a phase difference of about 90 degrees is output from each of the piezoelectric transformers 3 and 52. The AC output voltage of the piezoelectric transformers 3 and 52 is used as a drive voltage for driving the ultrasonic motor 43.

As shown in FIG. 15, in the ultrasonic motor 43 of the second embodiment, a plurality of piezoelectric ceramics 46 are arranged on the lower surface of a ring-shaped stator metal 45 so that the polarization directions are alternately reversed. This is a traveling wave type ultrasonic motor in which the rotor 47 is brought into contact with the upper surface of the ring-shaped stator metal 45. As shown in FIG. 16, two AC output voltages having a phase difference of 90 degrees from the piezoelectric transformers 3 and 52 (ie, a cosine wave and a sine wave) are respectively applied to the electrodes 48 of the piezoelectric ceramics 46 that are alternately reverse-polarized. Is applied. Then, the piezoelectric ceramics 46 vibrate, and the vibration excites the bending traveling wave traveling in the direction of the arrow K3 on the upper surface of the ring-shaped stator metal 45. At this time, the surface of the stator metal 45 moves in an elliptical trajectory as indicated by an arrow K5. Therefore, the rotor 47 in contact with the stator metal 45 is driven to rotate in the direction of arrow K4 by friction at the contact point.

The input impedance of the ultrasonic motor 43 is set to various values depending on the application. For example, in the case of the ultrasonic motor 43 having an output of about 4 watts, the driving voltage is 100 V, the rated current per phase is 53 mA, and the input impedance is about 2 kΩ. Therefore, in order to drive the ultrasonic motor 43, the piezoelectric transformer 3 and the piezoelectric transformer 52 are set so that the respective boosting ratios when the load resistance is 2 kΩ are substantially the same.

The ultrasonic motor driving device 51 having the above-described structure uses the piezoelectric transformers 3 and 52, so that the size thereof can be reduced, and the radiation of noise due to the magnetic flux generated in the conventional winding transformer can be reduced. Further, by using the piezoelectric transformers 3 and 52, two AC output voltages having a phase difference of 90 degrees can be supplied to the ultrasonic motor 43 without a phase shifter.
To drive the ultrasonic motor 43.

[Third Embodiment, FIGS. 17 to 21] FIG.
As shown in FIG. 7, the ultrasonic motor driving device 7 of the third embodiment
1 is an oscillator 2 and one two-output piezoelectric transformer 7
And 2. As shown in FIGS. 18 and 19, the piezoelectric transformer 72 includes one primary side driving unit 73,
It has two secondary power generation units 74 and 75 arranged on both sides of the primary drive unit 73.

The piezoelectric transformer 72 has a hot-side internal electrode 85a and a ground-side internal electrode 86a of the primary-side driving unit 73 formed on a ceramic green sheet, and a hot-side internal electrode 85b and a hot-side internal electrode 85b of the secondary-side power generation unit 74. A ground-side internal electrode 86b is formed, and these green sheets are laminated and pressed, cut into a square shape, sintered, and subjected to polarization processing in the directions of P1, P2, and P3. The internal electrodes 85a of the driving unit 73,
A gap of about 0.2 to 0.5 mm is secured between the internal electrode 86a and the internal electrodes 85b and 86b of the power generation unit 74 to prevent a short circuit.

The piezoelectric unit 81 has an input external electrode 7
6, a first output external electrode 78, a second output external electrode 80, and ground external electrodes 77 and 79 are formed. The input external electrode 76 is electrically connected to the hot-side internal electrode 85a, and the ground external electrode 77 is connected to the ground-side internal electrode 86a.
a. The first output external electrode 78 is electrically connected to the hot-side internal electrode 85b, and the ground external electrode 79 is electrically connected to the ground-side internal electrode 86b.

When an AC voltage is applied to the piezoelectric transformer 72 between the input external electrode 76 and the ground external electrode 77, the primary side drive section 73 excites vibration by a piezoelectric transverse effect. As a result, the first power generating unit 74 converts the vibration into electricity by the piezoelectric transverse effect, and generates a boosted AC output voltage between the first output external electrode 78 and the ground electrode 79,
In the second power generation unit 75, vibration is converted into electricity by the piezoelectric longitudinal effect, and a boosted AC voltage is generated between the second output external electrode 80 and the ground external electrode 77. That is, in the piezoelectric transformer 72, the driving unit 73 and the first power generation unit 74 use the piezoelectric horizontal effect, and the second power generation unit 75 uses the piezoelectric vertical effect. The driving section 73 and the first power generation section 74 constitute a first piezoelectric transformer section 82, and the driving section 73 and the second power generation section 75 constitute a second piezoelectric transformer section 83.

FIGS. 20 and 21 show a piezoelectric transformer 72.
Has a width of 6 mm, a thickness of 1.4 mm, and a length L of the driving unit 73.
1 is 6 mm, the length L3 of the first power generation unit 74 is 12 mm,
When the length L2 of the second power generation unit 75 is 12 mm, the number of internal electrodes of the driving unit 73 is 16 layers, the number of internal electrodes of the first power generation unit 74 is 8 layers, and the value of the load resistance is 2 kΩ. 5 is a graph showing respective boost ratios and phases of the first piezoelectric transformer unit 82 and the second piezoelectric transformer unit 83. FIG. 21 also shows the phase difference between the output voltage of the first piezoelectric transformer unit 82 and the output voltage of the second piezoelectric transformer unit 83 by a dashed line. As can be seen from FIGS. 20 and 21, near the resonance frequency (around 53.5 kHz) where the step-up ratio of the piezoelectric transformers 82 and 83 is maximum, the output voltages of the piezoelectric transformers 82 and 83 have a phase difference of about 90 degrees. Has occurred.

Therefore, by using one piezoelectric transformer 72, the two AC output voltages having a phase difference of 90 degrees are applied to the ultrasonic motor 43 without using a phase shifter to drive the ultrasonic motor 43. Can be.

The piezoelectric transformer 72 is not necessarily the one shown in FIG.
The structure is not limited to the structure shown in FIGS. 8 and 19, and the driving unit 7 utilizing the piezoelectric longitudinal effect as shown in FIG.
A similar effect can be obtained with a piezoelectric transformer 72A having a 3A or a piezoelectric transformer 72B in which the positions of the drive unit 73 and the power generation unit 74 are switched as shown in FIG. The drive unit 73A in FIG. 22 is configured such that an input external electrode 76 is electrically connected to a grid-like hot-side internal electrode 85a extending in the width direction of the piezoelectric body unit. It has a structure in which a ground external electrode 77 is electrically connected to 86a.

[Other Embodiments] The present invention is not limited to the above embodiment, but can be variously modified within the scope of the gist. For example, the material of the piezoelectric transformer may be any material having piezoelectricity such as a piezoelectric ceramic, a piezoelectric single crystal, and a piezoelectric polymer. Further, the ultrasonic motor driving device of the present invention can be applied to an actuator that operates a lever, a valve, or the like using an ultrasonic motor.

[0035]

As is clear from the above description, according to the present invention, the size of the ultrasonic motor driving device can be reduced by using the piezoelectric transformer. Further, by adopting effects in different directions, that is, a vertical effect and a horizontal effect, for the piezoelectric effect used in the power generation unit, an ultrasonic motor driving device can be configured without a phase shifter. Further, by employing a one-input multiple-output piezoelectric transformer, two or more AC output voltages having different phases can be supplied by one piezoelectric transformer, and the number of components can be reduced.

[Brief description of the drawings]

FIG. 1 is an electric block diagram showing a first embodiment of an ultrasonic motor driving device according to the present invention.

FIG. 2 is a schematic configuration diagram of the ultrasonic motor driving device shown in FIG.

FIG. 3 is an external perspective view of the piezoelectric transformer shown in FIG.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a sectional view taken along line VV of FIG. 3;

FIG. 6 is an electric block diagram showing a second embodiment of the ultrasonic motor driving device according to the present invention.

7 is an external perspective view of the piezoelectric transformer 52 shown in FIG.

8 is a sectional view taken along the line VIII-VIII in FIG. 7;

9 is a graph showing a boost ratio of the piezoelectric transformer 3 shown in FIG.

FIG. 10 is a graph showing the phase of a piezoelectric transformer 3;

11 is a graph showing a boost ratio of the piezoelectric transformer 52 shown in FIG.

FIG. 12 is a graph showing the phase of a piezoelectric transformer 52.

FIG. 13 is a graph showing the step-up ratio of each of the piezoelectric transformer 3 and the piezoelectric transformer 52 when the value of the load resistance is 2 kΩ.

FIG. 14 is a graph showing the phases of the piezoelectric transformer 3 and the piezoelectric transformer 52 when the value of the load resistance is 2 kΩ.

FIG. 15 is an external perspective view of the traveling wave type ultrasonic motor shown in FIG. 6;

FIG. 16 is a schematic configuration diagram of the ultrasonic motor driving device shown in FIG. 6;

FIG. 17 is an electric block diagram showing a third embodiment of the ultrasonic motor driving device according to the present invention.

18 is an external perspective view of the piezoelectric transformer shown in FIG.

FIG. 19 is a sectional view taken along line XIX-XIX in FIG. 18;

FIG. 20 is a graph showing the boost ratio of the piezoelectric transformer shown in FIG. 18 when the value of the load resistance is 2 kΩ.

FIG. 21 is a graph showing the phase of the piezoelectric transformer shown in FIG. 18 when the value of the load resistance is 2 kΩ.

FIG. 22 is a sectional view showing a modification of the piezoelectric transformer shown in FIG. 18;

FIG. 23 is a sectional view showing another modified example of the piezoelectric transformer shown in FIG. 18;

[Explanation of symbols]

 1, 51, 71: Ultrasonic motor drive device 2: Oscillator 3, 52, 72, 72A, 72B: Piezoelectric transformer 11, 59, 81 ... Piezoelectric unit 12, 53, 73, 73A: Primary drive unit 13, 54 , 74, 75 ... secondary side power generation part 14, 55, 76 ... input external electrode 15, 56, 58, 77, 79 ... ground external electrode 16, 57, 78, 80 ... output external electrode

Claims (4)

[Claims] An oscillator and one piezoelectric transformer are provided,
An ultrasonic motor driving device, wherein a driving voltage for driving a linear ultrasonic motor is generated by inputting an AC voltage from the oscillator to the one piezoelectric transformer. 2. An oscillator, a first piezoelectric transformer, and a second piezoelectric transformer, and an AC voltage from the oscillator is input to the first piezoelectric transformer, so that a piezoelectric lateral effect or a piezoelectric is applied to a primary side driving unit. A longitudinal effect is produced, and a piezoelectric longitudinal effect or a piezoelectric transverse effect is produced in the secondary-side power generation section, thereby generating a first drive voltage for the traveling wave type ultrasonic motor and the second piezoelectric element. By inputting an AC voltage from the oscillator to the transformer, a piezoelectric effect in the same direction as the primary drive unit of the first piezoelectric transformer is generated in the primary drive unit, and the secondary power generation unit is provided with the piezoelectric effect. First
A piezoelectric effect in a direction different from that of the secondary-side power generation section of the piezoelectric transformer to generate a second drive voltage for the traveling wave type ultrasonic motor, and the first drive voltage and the second drive voltage are generated. An ultrasonic motor driving device, wherein a voltage phase difference is approximately 90 degrees. 3. An oscillator and one piezoelectric transformer,
The piezoelectric transformer has at least one input terminal and at least two output terminals, and by inputting an AC voltage from the oscillator to the input terminal, the traveling-wave type supersonic wave is output from at least two output terminals. An ultrasonic motor driving device for outputting a first driving voltage and a second driving voltage of an ultrasonic motor, wherein a phase difference between the first driving voltage and the second driving voltage is approximately 90 degrees. 4. An oscillator and one piezoelectric transformer,
The piezoelectric transformer has at least one primary-side drive unit and at least two secondary-side power generation units, and generates an piezoelectric lateral effect or a piezoelectric longitudinal effect by inputting an AC voltage from the oscillator to the primary-side drive unit. Causing a piezoelectric longitudinal effect in at least one of the secondary-side power generation units to generate a first drive voltage for the traveling wave type ultrasonic motor, and in at least one of the other secondary-side power generation units. A second driving voltage for the traveling wave type ultrasonic motor is generated by generating a piezoelectric transverse effect, and a phase difference between the first driving voltage and the second driving voltage is approximately 90 degrees. Ultrasonic motor drive device.