JP2000166265A - Vibration-type actuator driving apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vibration-type actuator driving apparatus in which the number of components is small, which realizes a low-cost constitution and which can step up a driving voltage more. SOLUTION: In this vibration-type actuator driving apparatus, both terminals of an inductance element 6 in which a center tap is installed are connected to two electrodes which sandwich an electromechanical energy conversion element, and the center tap is connected to a DC power supply Vbat. In addition, both terminals of the inductance element 6 are connected to sides, on one side, of two switching elements FET1, FET2, and sides, on the other side, of the switching elements FET1, FET2 are grounded, Then, a logic part alternately changes over the continuity of the two switching elements FET1, FET2. A state that one of the two elements which sandwich the electromechanical energy conversion element is grounded and that the other floats and its opposite state are changed over alternately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration-type actuator driving device, and more particularly to a vibration-type actuator driving device that obtains a driving force by being excited by applying a frequency signal to an electro-mechanical energy conversion element.

[0002]

2. Description of the Related Art Recently, a vibration type (vibration wave) actuator called an ultrasonic motor or a piezoelectric motor has been developed and has been put to practical use by the present applicants.

As is well known, this vibration wave motor generates a high frequency vibration by applying an alternating voltage to an electro-mechanical energy conversion element such as a piezoelectric element or an electrostriction element. This is a new type of non-electromagnetic drive motor configured to extract vibration energy as continuous mechanical motion. The principle of this operation is described in
Since it is described in, for example, Japanese Unexamined Patent Publication No. -289375, the description is omitted here.

FIG. 11 is a diagram showing the configuration of a conventional bar-shaped ultrasonic motor and a vibrating body. Reference numeral 101 denotes a vibrating body constituting the rod-shaped ultrasonic motor, which is formed by a combined body of a piezoelectric element and an elastic body. 102 is a rotor.

The piezoelectric element of the vibrating body 101 has a driving A
Phase piezoelectric elements a1, a2 and B phase piezoelectric elements b1, b2
And a vibration detecting piezoelectric element s1. An electrode Ad is provided between the A-phase piezoelectric elements a1 and a2,
An electrode Bd is provided between the phase piezoelectric elements b1 and b2,
In addition, three electrodes GND-d for grounding are provided, and a signal extraction electrode Sd is provided for the vibration detecting piezoelectric element S1.

In such a configuration, the A-phase piezoelectric element a
The piezoelectric elements are driven by applying the A-phase signal voltage to the electrodes Ad sandwiched between the electrodes 1 and a2 and the B-phase signal voltage to the electrodes BD sandwiched between the B-phase piezoelectric elements b1 and b2. . In the vibration detecting piezoelectric element S1, an output voltage corresponding to the vibration is output from the signal extraction electrode S-d. The signal extraction electrode S-
Although d is in contact with the metal block, the metal block is insulated from the ground potential by the insulating sheet. Therefore, the output voltage corresponding to the vibration is directly obtained from the vibration detecting piezoelectric element S1. Then, the magnitude of the output voltage, the phase difference between the output voltage and the drive voltage, and the like are used for vibration control.

FIG. 12 is a circuit diagram showing a conventional drive circuit for such an ultrasonic motor.

The A-phase and B-phase signal voltages, which are alternating voltages, are applied to each piezoelectric element via drive electrodes Ad and Bd and a ground electrode GND-d. In the figure, 11 is a control circuit for driving and controlling the ultrasonic motor, 2 is an oscillator for generating an alternating voltage (for example, a VCO), 3 is a 90 ° phase shifter, 4 and 5 are the oscillator 2 and the phase shifter. Switching circuits 31 and 32 for switching the power supply voltage with the alternating voltage from the switch 3, and inductance elements 31 and 32 for matching the impedance with the ultrasonic motor. Reference numeral 8 denotes a phase difference detector that detects a signal phase difference θA-S between the drive signal A output from the inductance element 31 and the vibration detection signal S output from the signal extraction electrode Sd.

Conventionally, a piezoelectric element requires a relatively high drive voltage, and the switching circuits 4 and 5 switch and boost a power supply voltage of several tens of volts.

That is, the switching circuits 4 and 5 alternately switch the potential of each end of the inductance elements 31 and 32 between the power supply voltage and the ground potential. That is, when the potential at one end of the inductance element 31 is the power supply voltage, the potential at one end of the inductance element 32 is set to the ground potential. When the potential at one end of the inductance element 31 is the ground voltage, the potential at one end of the inductance element 32 is set to the power supply voltage. And With this switching, the inductance element 31,
At 32, high voltages having phases shifted from each other by 180 degrees are induced, and these are applied to the piezoelectric element.

[0011]

In the conventional driving circuit shown in FIG. 12, one electrode of each piezoelectric element is always grounded, and the induced voltage is applied to the other electrode. Configuration. Therefore, it cannot be said that a high driving voltage is always obtained in the conventional driving circuit shown in FIG. Switching circuits 4 and 5
Requires four switching elements, and has a problem that the circuit becomes complicated and the cost increases.

[0012] For example, Japanese Patent Application Laid-Open No. 10-146072 discloses a drive circuit of an ultrasonic motor which performs boosting by switching by a full bridge circuit using four switching elements. As many as eight switching elements are required for one ultrasonic motor, the circuit becomes more complicated, and the cost increases.

Further, in the device disclosed in Japanese Patent Application Laid-Open No. 9-163767 (only one phase is shown for convenience) as shown in FIG. 13, the switching element 13 is connected to the inductance element 12 to which the power supply voltage Vbat is applied. The connection point is connected to one of the electrodes sandwiching the piezoelectric element 14. Therefore, in this device, only two switching elements are required for two piezoelectric elements, but there is a problem that a sufficient boosting rate cannot be obtained as compared with a circuit using a full bridge.

The present invention has been made in view of the above problems, and provides a vibration-type actuator driving device which has a small number of parts, is inexpensive, and can further increase the driving voltage. The purpose is to do.

[0015]

To achieve the above object, according to the first aspect of the present invention, a vibration type in which a driving signal is excited by applying a frequency signal to an electro-mechanical energy conversion element to thereby excite the element. In the actuator driving device, an electro-mechanical energy conversion element sandwiched between two electrodes and a center tap are provided, and both terminals are connected to an inductance element connected to the two electrodes sandwiching the electro-mechanical energy conversion element. A DC power supply connected to a center tap of the inductance element, two switching elements each having one side connected to both terminals of the inductance element, and grounding the other side, and conducting the two switching elements. A state in which one of two electrodes sandwiching the electro-mechanical energy conversion element is alternately switched to ground and the other is floating. , And having a drive control means for switching between the opposite state alternately.

According to the fifth aspect of the present invention, in a driving device of a vibration type actuator for obtaining a driving force by exciting by applying a frequency signal to an electro-mechanical energy conversion element, the device is sandwiched between two electrodes. An electro-mechanical energy conversion element, and two inductance elements each having one terminal connected to a DC power supply and each other terminal connected to two electrodes sandwiching the electro-mechanical energy conversion element,
The two switching elements, one of which is connected to the other terminal of the two inductance elements, and the other of which is grounded, alternately switch the conduction of the two switching elements, thereby providing the electro-mechanical energy conversion. 2 sandwiching the element
One of the two electrodes is grounded, and the other has a drive control means for alternately switching between a floating state and an opposite state.

[0017]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a diagram showing a configuration of an ultrasonic motor according to a first embodiment of the present invention. In FIG. 1, the same components as those of the conventional configuration shown in FIG. 11 are denoted by the same reference numerals, and description thereof will be omitted.

In FIG. 1, electrodes Ad, A'-d, B
-D and B'-d are provided so as to sandwich the piezoelectric elements a1 and b1, respectively. The piezoelectric elements a1 and b1 are driven by a four-phase driving voltage (A, A ', B, and B' described later in FIG. 2). ). In the present invention, there is no common electrode for ground (GND). In this configuration, the electrode plates Ad,
By supplying the drive voltages with inverted phases to A′-d, Bd, and B′-d, the number of piezoelectric elements is reduced from two to one in FIG. This ultrasonic motor can be driven by the same power supply voltage as in the case of the conventional configuration shown in FIG.

FIG. 2 is a circuit diagram showing a drive circuit of the ultrasonic motor shown in FIG. Here, the same components as those of the conventional circuit shown in FIG. 12 are denoted by the same reference numerals, and the description thereof will be omitted.

In the first embodiment, the switching elements in the switching circuits 10 and 10 'are replaced by FETs (FET1, FET2,
FET1 ', FET2').

The sources of FET1 and FET2 are grounded, and a control signal is sent to the gate from the logic unit. Similarly, the sources of FET1 'and FET2' are grounded, and a control signal is sent from the logic unit to the gate. In addition, each F
A reverse current passing diode is provided between the drain and the source of the ET. The provision of this diode prevents the FET from being damaged by the reverse current.

Reference numerals 6, 6 ', 7, and 7' denote impedance elements for performing impedance matching with the ultrasonic motor. In this example, 6 and 7 are inductance elements,
6 'and 7' are capacitance elements. 6,6 ',
By adding impedance elements at the positions of 7, 7 ', the ultrasonic motor can be driven with lower voltage and higher efficiency (the capacitance elements 6', 7 'need not always be added). ).

The inductance element 6 has its midpoint connected to the DC power supply Vbat, both ends connected to the drain of the FET1 and the drain of the FET2, and the electrodes A-d and A'-d sandwiching the piezoelectric element a1. Connected to.
Similarly, the midpoint of the inductance element 7 is
bat, both ends of which are connected to the drain of FET1 'and the drain of FET2', respectively, and to the electrodes B-d and B'-d sandwiching the piezoelectric element b1.

FET constituting switching circuit 10
1, FET2 operates under the control of the logic unit,
When the FET1 is ON and the FET2 is OFF, the A signal is set to a low potential and the A 'signal is set to a high potential. On the other hand, FET2
Is ON and the FET1 is OFF, the A signal is set to a high potential and the A 'signal is set to a low potential. Therefore, the O
N, OFF state of FET2 and OFF, F of FET1
By alternately repeating the ON state of ET2 by the logic unit of the switching circuit 10, an A signal and an A 'signal whose phases are shifted by 180 degrees as shown in FIG. 3 are obtained.

In the switching circuit 10 ', the logic portion of the switching circuit 10' is an FET.
1 'and the FET 2' are controlled in the same manner as the switching circuit 10, and a B signal and a B 'signal whose phases are shifted by 180 degrees as shown in FIG. 3 are obtained. The logic portion of the switching circuit 10 'includes a B signal, B'
The signals are controlled so that their phases are delayed or advanced by 90 degrees with respect to the A signal and the A 'signal of the switching circuit 10, respectively. FIG. 3 exemplifies a case of being late.

The voltage applied to each of the piezoelectric elements a1 and b1 is the potential difference between the A signal potential and the A 'signal potential, and B
It is the potential difference between the signal potential and the B 'signal potential.

FIG. 3 is a timing chart of each signal. In the figure, AA 'and BB' indicate the potential difference between the A signal potential and the A 'signal potential, and the B signal potential and the B' signal, respectively. Indicates the potential difference from the potential. As can be seen, the piezoelectric elements a1 and b1 have a phase difference of 90 degrees and the signals A and b.
A drive voltage having twice the amplitude of A ', B, B' is applied.

A signal dir for instructing normal rotation and reverse rotation is input from the control circuit 11 to the switching circuit 10 '. The logic part of the switching circuit 10 '
When receiving the signal dir indicating the normal rotation, the B signal,
The B ′ signal is controlled so that the phases thereof are delayed by 90 degrees with respect to the A signal and the A ′ signal of the switching circuit 10, respectively.
The control is performed so that the B 'signal leads the A signal and the A' signal of the switching circuit 10 by 90 degrees.

Next, the driving circuit according to the first embodiment is
Let's compare it with a conventional drive circuit.

In the driving circuit (FIG. 13) disclosed in Japanese Patent Application Laid-Open No. 9-163767, the voltage applied to the piezoelectric element 14 has a waveform shown in FIG. On the other hand, in the first embodiment, since there is also an effect by magnetic coupling, a boosting effect approximately twice as high as that of the conventional circuit shown in FIG. 13 can be obtained. Further, in the driving circuit described in JP-A-9-163767 shown in FIG. 12, since only one side of the DC power supply is used, the driving circuit is similar to the driving circuit (FIG. 13) shown in JP-A-9-163767. The boosting effect is inferior to that of the drive circuit of the first embodiment.

FIG. 4 shows the invention shown in the first embodiment.
FIG. 1 is a diagram illustrating a drive circuit when applied to a full-bridge drive circuit disclosed in Japanese Patent Application Laid-Open No. 10-146072. In the figure, parts having the same functions as those of the drive circuit shown in FIG. 2 are denoted by the same reference numerals.

The circuit shown in FIG. 4 has a boosting effect substantially equal to that of the drive circuit shown in FIG. However, compared to the drive circuit shown in FIG.
And two extra inductance elements are required, which complicates the circuit.

As described above, in the first embodiment of the present invention, it is possible to obtain a driving circuit having a high boosting rate while having a simple circuit configuration as compared with a conventional driving circuit.

Next, the structure of the inductance elements 6 and 7 will be described.

FIG. 5 is a diagram showing the structure of an inductor with a center tap used for the inductance elements 6 and 7.

As shown in FIG. 5, the inductance elements 6 and 7 are bifilar-wound inductors in which two conductors L1 and L2 are superposed and wound on a core material 15. And
One end A-2 of the conductor L1 is connected to the other end A which is not adjacent to the conductor L2.
-1 and take out the center tap CT from the connection point. Thereby, an inductor with a center tap with good coupling can be obtained.

This inductor has a circuit symbol as shown in the upper part of FIG. 6, and the mutual inductance works in the boosting direction and can regenerate energy, so that the efficiency is improved and the boosting effect can be improved. FIG.
6 differs from the structure shown in FIG. 6 in that adjacent ends of the conductor L1 and the conductor L2 are connected to each other to form a center tap.
In the first embodiment, such an inductor cannot be used because the mutual inductance acts in the direction to cancel the boost, contrary to the first embodiment.

In the first embodiment, for the sake of convenience, a rod-type ultrasonic motor has been described as an example, but the present invention is also applicable to a ring-type ultrasonic motor as shown in FIG. It is possible. That is, in the ring type ultrasonic motor, 27 is a rotor, 28 is a pressing member, 29 is a stator, 30 is a piezoelectric element, and the piezoelectric element 30 is
Is glued. Each of the phase electrodes for applying a drive voltage to the piezoelectric element 30 is not provided with a common electrode, and can be applied in a similar manner by floating the piezoelectric element 30 from the ground potential.

(Second Embodiment) FIG. 8 is a diagram showing a drive circuit of an ultrasonic motor according to a second embodiment of the present invention. FIG. 8 shows only one phase portion for convenience, but there is actually another phase portion having a similar configuration.

The power supply voltage Vbat is applied to one end of each of the inductors 16 and 17, and the switching circuit 1 is connected to the other end.
8 and 19 are respectively connected. Switching circuit 1
8 and 19 are each composed of one switching element. A piezoelectric element 23 is provided between a connection point between the inductor 16 and the switching circuit 18 and a connection point between the inductor 17 and the switching circuit 19 via an electrode. Further, a capacitance element 20 is connected to both electrodes.

The inductors 16 and 17 are set to values whose impedance matches the piezoelectric element 23 and the capacitance element 20. The capacitance element 20
It is not always necessary to add.

The switching circuits 18 and 19 operate in the same manner as in the first embodiment. Also in this circuit, the A signal, the A 'signal, and the potential difference A- between the A signal potential and the A' signal potential.
A 'is the same as that of the first embodiment shown in FIG. 3, and therefore, it is possible to obtain a drive circuit having a higher boosting rate than the conventional example.

In the second embodiment, as compared with the first embodiment, the number of inductors is increased by two per ultrasonic motor. However, since a center tap is not required for the inductor, a general-purpose inductor is used. There is an advantage that can be.

As shown in FIG. 9, by providing an appropriate coupling between the two inductors 21 and 22, energy can be regenerated and the efficiency can be further increased. FIG. 9 shows the second embodiment shown in FIG.
FIG. 7 is a diagram showing an example in which two inductors 16 and 17 have mutual induction (M) coupling.

When connecting the two inductors 21 and 22, it is necessary to pay attention to the polarity of the inductors.
That is, the voltages generated by the mutual induction are made to be opposite to each other.

The second embodiment can be applied to a rod-shaped ultrasonic motor or a floating type of an annular type motor as shown in FIG.

(Third Embodiment) FIG. 10 is a sectional view showing a driving apparatus for driving a lens using an ultrasonic motor having a driving circuit according to the present invention.

The rod-shaped ultrasonic motor 1 includes a drive circuit according to the present invention.
The gear f meshes with the input gear GI of the gear transmission mechanism G, and the output gear GO of the gear transmission mechanism G is a gear formed on the lens holding member H that holds the lens L1. It is engaged with HI. The lens holding member H is helicoidally coupled to the fixed barrel K, and is driven to rotate by the driving force of the ultrasonic motor 1 via the gear transmission mechanism G to perform a focusing operation.

[0050]

As described in detail above, according to the present invention,
An electro-mechanical energy conversion element sandwiched between two electrodes,
A center tap is provided, both terminals of which are connected to two electrodes sandwiching the electro-mechanical energy conversion element, a DC power supply connected to a center tap of the inductance element, and both terminals of the inductance element. Two switching elements each having one side connected thereto and the other side grounded, and alternately switching the conduction of the two switching elements so that one of two electrodes sandwiching the electro-mechanical energy conversion element is grounded. And a drive control means for alternately switching between a state where the other is floating and a state where the other is floating.

With such a configuration, the vibration-type actuator driving device can be configured with a smaller number of parts as compared with the conventional one, so that the product cost is reduced and the inductance element having the center tap is provided. Further, the drive voltage can be sufficiently increased by the drive control means.

Also, an electro-mechanical energy conversion element sandwiched between two electrodes, and one terminal connected to a DC power supply,
Two other terminals are respectively connected to two electrodes sandwiching the electro-mechanical energy conversion element, and one side is connected to each of the other terminals of the two inductance elements, and the other side is connected to each other. A state in which one of two electrodes sandwiching the electro-mechanical energy conversion element is grounded and the other is floating, and the opposite is performed by alternately switching two grounded switching elements and conduction of the two switching elements. And drive control means for alternately switching between the states.

With such a configuration, the vibration-type actuator driving device can be configured with a smaller number of parts compared with the conventional one, and a general-purpose inductance element can be used. The drive voltage can be reduced, and the drive voltage can be sufficiently increased by the two inductance elements and the drive control means.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an ultrasonic motor according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a drive circuit according to a first embodiment for driving the ultrasonic motor shown in FIG.

FIG. 3 is a timing chart of each signal.

FIG. 4 shows the invention shown in the first embodiment,
FIG. 2 is a diagram showing a drive circuit when applied to the drive circuit disclosed in Japanese Patent No. 146072.

FIG. 5 is a diagram showing a structure of an inductor with a center tap.

FIG. 6 is a diagram showing a circuit symbol of an inductor.

FIG. 7 is a cross-sectional view showing a configuration of a ring-type ultrasonic motor.

FIG. 8 is a diagram showing a drive circuit of an ultrasonic motor according to a second embodiment of the present invention.

FIG. 9 is a diagram showing an example in which two inductors have mutual induction coupling in the second embodiment shown in FIG. 8;

FIG. 10 is a cross-sectional view illustrating a driving device according to a third embodiment for driving a lens using an ultrasonic motor including a driving circuit according to the present invention.

FIG. 11 is a diagram showing a configuration of a conventional bar-shaped ultrasonic motor and a vibrating body.

FIG. 12 is a circuit diagram showing a driving circuit of a conventional ultrasonic motor.

FIG. 13 is a diagram showing a conventional drive circuit disclosed in Japanese Patent Application Laid-Open No. 9-163767.

FIG. 14 is a diagram showing a waveform of a voltage applied to a piezoelectric element in a conventional driving circuit disclosed in Japanese Patent Application Laid-Open No. 9-163767.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ultrasonic motor 2 Oscillator 3 Phase shifter 4 Switching circuit 5 Switching circuit 6 Inductance element 6 'Capacitance element 7 Inductance element 7' Capacitance element 8 Phase difference detector 10 Switching circuit 10 'Switching circuit 11 Control circuit (drive control means) 14 Piezoelectric element 27 Rotor 28 Pressing member 29 Stator 30 Piezoelectric element 101 Vibrating body 102 Rotor a1 Piezoelectric element a2 Piezoelectric element b1 Piezoelectric element b2 Piezoelectric element S1 Piezoelectric element Ad electrode A'-d electrode BD electrode B '-D electrode Sd Vibration detection electrode GND-d Grounding electrode

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H680 AA00 AA01 AA08 BB01 BB16 BC01 CC10 DD01 DD15 DD23 DD27 DD39 DD53 DD66 DD83 DD87 EE12 FF08 FF26 FF33 FF35

Claims (8)

[Claims] A driving device for a vibration-type actuator that obtains a driving force by applying a frequency signal to an electro-mechanical energy conversion element to obtain a driving force, comprising: an electro-mechanical energy conversion element sandwiched between two electrodes; A tap is provided, and both terminals are connected to two electrodes sandwiching the electro-mechanical energy conversion element; a DC power supply connected to a center tap of the inductance element; and both terminals of the inductance element. Two switching elements, each connected on one side, and the other side grounded, alternately switches the conduction of the two switching elements, and one of two electrodes sandwiching the electro-mechanical energy conversion element is grounded. , The other is floating,
And a drive control means for alternately switching between the opposite state and the opposite state. 2. The vibration-type actuator driving device according to claim 1, further comprising a capacitance element having both terminals connected to both terminals of said inductance element. 3. The vibration type actuator according to claim 1, wherein the drive control unit supplies a switching signal having a phase difference of 180 degrees to the two switching elements. Drive. 4. The inductance element is formed by bifilar winding of first and second conductors, and one end of the first conductor and the one end of the first conductor in the second conductor are connected to each other. 4. The vibration-type actuator driving device according to claim 1, wherein the other end on the opposite side is connected, and the connection point is a center tap. 5. A driving device for a vibration-type actuator, which obtains a driving force by exciting a frequency signal by applying a frequency signal to the electro-mechanical energy conversion element, comprising: an electro-mechanical energy conversion element sandwiched between two electrodes; One terminal is connected to a DC power supply, and each other terminal is connected to two electrodes each sandwiching the electro-mechanical energy conversion element, and two inductance elements are connected to each other. The two switching elements whose sides are connected and the other sides of which are grounded alternately switch the conduction of the two switching elements, and one of two electrodes sandwiching the electro-mechanical energy conversion element is grounded, and the other is grounded. Is floating,
And a drive control means for alternately switching between the opposite state and the opposite state. 6. The vibration-type actuator driving device according to claim 5, further comprising a capacitance element having its own terminal connected to both terminals of said electro-mechanical energy conversion element. 7. The vibration type actuator according to claim 5, wherein the drive control unit supplies a switching signal having a phase difference of 180 degrees to the two switching elements. Drive. 8. The method according to claim 5, wherein the two inductance elements have a mutual inductive coupling relationship with each other, and polarities of terminals connected to a DC power supply are opposite to each other. The vibration type actuator driving device according to any one of the above.