JP2001258279A - Driver for vibration actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prolong the service life of a battery when an ultrasonic actuator is driven by a battery by overcoming the problem that electric energy cannot be used efficiently due to the condition that two equal AC voltage (drive signals) are applied to a piezoelectric body in spite of the fact that the phases have a relationship of being advanced and delayed in the conventional drive of a ultrasonic actuator. SOLUTION: This driver includes an electrical-to-mechanical conversion element 12 having an elastic body 11 and a plurality of electrodes 12a to 12d joined to the elastic body 11, and a control unit for generating a vibration on the elastic body by applying a first phase AC voltage and a second phase AC voltage having a delayed phase than the first phase to a plurality of electrodes 12a to 12d. In driving the vibration actuator by generating a relative motion between the elastic body 11 and the relative motion member 15 facing the elastic body 11, a current inputted with the AC voltage of the first phase is made different from the current inputted with the AC voltage of the second phase at the time of driving.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration actuator. More specifically, the present invention relates to a vibration actuator that performs relative motion by vibration generated by applying an AC voltage to an electromechanical transducer (eg, a piezoelectric element, an electrostrictive element, and the like, hereinafter, referred to as a piezoelectric element).

[0002]

2. Description of the Related Art Conventionally, as this kind of vibration actuator, an ultrasonic actuator utilizing an ultrasonic vibration region is known. In an ultrasonic actuator, an ultrasonic actuator that obtains a driving force by applying an AC voltage to a piezoelectric element bonded to an elastic body to generate longitudinal vibration and bending vibration in the elastic body in harmony has been developed. In the “Piezoelectric Linear Motor for Moving Optical Pickup” (Yoshiaki Tomikawa et al .: Proceedings of the 5th Electromagnetic Force-Related Dynamic Symposium, p. 393-398), the configuration and load characteristics are “New Ultrasonic Motor” ( A self-propelled apparatus is shown in Ueha Sadayuki and Tomikawa Yoshiro, published by Trikeps, pages 145 to 146). This actuator is shown in FIG.
Has an elastic body 11 in the form of a flat plate as shown in FIG.

[0003]

(Equation 1)

[0004]

(Equation 2)

The resonance frequency of the first-order longitudinal vibration mode and the resonance frequency of the fourth-order bending vibration mode are designed to be very close to each other. The control unit has the configuration shown in FIG. Each part will be described below. Oscillator 2
Numeral 1 outputs two drive signals of A-phase and B-phase which are close to the resonance frequencies of the two modes. The B-phase drive signal is delayed by 90 ° (π / 2) phase by the phase shifter 22 and then the amplifier 23
The signal is amplified by -2 and input to the electrodes 12b and 12d on the piezoelectric element. On the other hand, the A-phase drive signal is supplied from the oscillator 21 to the phase shifter 2.
2, the phase is output to the amplifier 23-1 without change, and after being amplified, the electrodes 12a, 12a
c. Thus, two AC voltages having frequencies close to the resonance frequency and having a phase difference of 90 ° are applied to the electrodes 12a and 12c on the piezoelectric element and the electrodes 12b and 12b on the piezoelectric element.
12d, the first order longitudinal vibration mode and the fourth mode bending vibration are generated harmoniously in the elastic body, and the protrusions provided at two outer positions among the four antinode positions of the bending vibration. The tips of the portions 13a and 13b perform an elliptical motion to obtain a driving force. The driving direction can be changed by reversing the phase relationship between the two AC voltages to be applied. FIG.
Is a document showing driving characteristics when the vibration actuator is driven under the following conditions. (Conditions) Elastic body shape 50mm (length in the relative movement direction) x 10mm (width) x 3mm (thickness) Elastic body material Stainless steel Electromechanical conversion element material Lead zirconate titanate (PZT) Electrode shape 10mm x 8mm, 4 pieces Input voltage: about 30 Vrms Driving frequency: about 47 KHz In FIG. 7A, the current indicates the total current flowing into the electrodes of the ultrasonic actuator. In FIG. 7B, the characteristic indicated by a dotted line connecting diamond points indicates the total current flowing into the electrode, and the characteristic indicated by a broken line connecting square points indicates the moving speed of the relative motion member. , And the characteristic indicated by the solid line connecting the triangular points indicates the driving efficiency. As described above, conventionally, the efficiency is up to about 16%.

[0006]

Conventionally, when driving an ultrasonic actuator, two AC voltages (driving signals) are applied to the piezoelectric body at the same voltage despite having a phase-advance relationship in phase. . Therefore, they did not always use electric energy efficiently. On the other hand, the ultrasonic actuator may be driven by a battery or the like. In the case of a battery-driven ultrasonic actuator, if the electric energy cannot be used efficiently, the life of the battery may be shortened, which may hinder practical use.

[0007]

According to the first aspect of the present invention, there is provided an electromechanical transducer element having an elastic body and a plurality of electrodes joined to the elastic body and having a plurality of electrodes. A control unit that applies a first-phase AC voltage and a second-phase AC voltage delayed in phase from the first phase to the electrodes 12a to 12d to generate vibration in the elastic body; When a relative motion is generated between the elastic body 11 and the relative motion member 15 to drive the vibration actuator, the current flowing in by the first-phase AC voltage and the second
The drive is made different from the current flowing in according to the AC voltage of the phase.

According to the invention described in claim 2, the control unit 6
0 vibrates in the same direction as the direction of relative movement as vibration 1
The driving device according to claim 1 is a vibration actuator that is a vibration in which the next vertical vibration and a fourth-order bending vibration that vibrates in a direction substantially perpendicular to the vibration surface of the vertical vibration are combined.

According to the third aspect of the present invention, the first aspect is provided.
Alternatively, in the invention described in the second aspect, the control unit 60 performs the adjustment by at least one of the area of the portion to which the AC voltage is applied and the value of the applied voltage.

In the invention according to claim 4, when the number of electrodes to which the AC voltage is applied is four, the AC voltage of the first phase (the phase whose phase is advanced) is applied to two of the four electrodes. Then, the AC voltage application force is adjusted by applying an AC voltage of the second phase (a phase with a delayed phase) to one of the four electrodes.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
The present invention will be described in more detail with reference to embodiments. In each of the embodiments described below, an ultrasonic actuator that operates in the ultrasonic region will be described as an example of the vibration actuator, but the present invention is not limited to the ultrasonic actuator. (First Embodiment) FIG. 1 is a perspective view showing a driving section of an ultrasonic actuator according to the present invention. FIG. 3 is a block diagram illustrating a configuration of a control unit of the ultrasonic actuator according to the first embodiment of the present invention.

The driving unit 10 of the ultrasonic actuator according to the first embodiment includes an elastic body 11, a piezoelectric element 12 for generating vibration in the elastic body, and electrodes 12a to 12d for applying an AC voltage to the piezoelectric element 12. And projections 13a and 13b for transmitting a driving (relative movement) force to the relative movement member 15.

In this embodiment, the elastic body 11 is made of SUS304.
However, the elastic body may be made of a metal material having a large resonance sharpness, such as steel, phosphor bronze, or an elinvar material. The size of the elastic body 11 is such that the primary longitudinal vibration L1 vibrates in substantially the same direction as the generated relative movement direction and the fourth-order bending vibration vibrates in a direction substantially perpendicular to the vibration plane of the primary longitudinal vibration L1. The natural frequencies of B4 are set so as to be substantially the same.

A piezoelectric element 12, which is an electromechanical transducer, is adhered to one plane of the elastic body 11. Also, two square rod-shaped protrusions 13a and 13b are bonded to the other plane of the elastic body 11 in the width direction of the elastic body 11. Projection 1
3a and 13b are sliding members mainly composed of a polymer material or the like. PTFE, irimid resin, PE
N, PPS, PEEK and the like are exemplified. Also, the elastic body 1
1 may be provided with a groove, and the protrusions 13a and 13b may be fitted.

The protrusions 13a and 13b are
Is provided so as to coincide with the outer two antinode positions of the four antinode positions of the fourth-order bending vibration B4.
The protrusions 13a and 13b do not need to be provided at positions exactly matching the two antinode positions, but may be provided near these antinode positions. In this embodiment, the piezoelectric element 12 is made of thin plate-like PZT (lead zirconate titanate). This piezoelectric element 12 has four electrode portions 1
2a to 12d are provided, and a lead wire for applying a drive signal is soldered to each electrode. A phase (first phase) and B phase (second phase)
The phase (phase) drive signal is applied to the piezoelectric element 12 to generate vibration. In this embodiment, a silver electrode is used as the electrode.

The electrodes 12a to 12d are provided at the antinodes of the fourth-order bending vibration B4.
By applying a drive signal having a phase shift of (π / 2), the first-order longitudinal vibration L1 and the fourth-order bending vibration B4 are generated harmoniously in the elastic body 11. Fourth-order bending vibration B
Reference numeral 4 denotes a vibration having a clutch-like function between the relative movement member 15 and the projections 13a and 13b, and it is known that the primary longitudinal vibration L1 is a vibration having a function of generating a driving force. In the present embodiment, efficient driving is performed by reducing the voltage of a signal with a delayed phase, which is input to a circuit having a small impedance among the signals applied to the electrodes 12a to 12d. Due to the harmonic vibration generated in the elastic body 11, an elliptical motion is generated at the tips of the protrusions 13a and 13b. The protrusion 13 is in pressure contact with the relative movement member 15 by a biasing member (not shown), and drives the relative movement member 15 by the generated elliptical movement. The relative movement member 15 of the present embodiment is formed in a strip shape from stainless steel, but may be formed from a copper alloy, an aluminum alloy, a polymer material, or the like.

As shown in FIG. 3, the driving device 2 of this embodiment
0 is an oscillator 21, a phase shifter 22, an amplifier 23-1,
23-2 and switches 24-1 and 24-2. The oscillator 21 outputs a drive signal (AC voltage) in a frequency-variable manner, and the variable range is a range including the respective resonance frequencies of the primary longitudinal vibration L1 and the quaternary bending vibration B4 of the elastic body 11. ing. A-phase and B-phase having a frequency slightly higher than the natural frequency of any of the primary longitudinal vibration L1 and the fourth-order bending vibration B4 output from the oscillator 21
The phase B drive signal of the phase drive signals is
The phase is shifted by 90 ° (−π / 2) and input to the amplifier 23-2. On the other hand, the A-phase drive signal is output from the oscillator 21 and then input to the phase shifter 22, but is input to the amplifier 23-1 without changing the phase shift.

In the amplifiers 23-1 and 23-2, the input drive signal is amplified to a voltage that causes the piezoelectric element 12 to vibrate and cause the elastic body 11 to vibrate in a desired manner. The amplifier 2
The amplification factors of 3-1 and 23-2 are almost the same.

The positions of the electrodes to be applied to the drive signals output from the amplifiers 23-1 and 23-2 are determined by the switches 24-1 and 24-2 according to the moving direction. Switch 24-
When the switch 24-1 is a contact, the switch 24-2 is also a contact (mode 1). When the switch 24-1 is a contact, the switch 24-2 is also a contact. (Mode 2). By switching between mode 1 and mode 2,
The relative movement direction is switched.

Switch 2 when mode 1 is selected
4-1 and 24-2 are both short-circuited with the contacts, and the amplified A-phase drive signal is applied to the electrodes 12a and 12c.
The amplified B-phase drive signal is applied only to the electrode 12b. When mode 2 is selected, switch 2
4-1 and 24-2 are both short-circuited with the contacts, and the amplified A-phase drive signal is applied to the electrodes 12b and 12d.
The amplified B-phase drive signal is applied only to the electrode 12c. That is, by switching between mode 1 and mode 2, the phase relationship of the drive signals applied to the electrodes 12a, 12c and 12b, 12d is reversed, and the relative movement direction is switched.

As described above, in this embodiment, the B-phase drive signal whose phase is delayed with respect to the A-phase is applied to one of the four electrodes, and the A-phase drive signal is applied to the four electrodes. Are applied to two of the electrodes. Also, it has been found experimentally that the impedance of a circuit to which a delayed phase is input is smaller than the impedance of a circuit whose phase is advanced. Therefore, it has been found that a large voltage is consumed in a circuit to which a delayed phase is input when an AC voltage is applied in the same manner.

In this embodiment, the A-phase (first phase)
The phase (phase) drive signal is applied to two of the four electrodes, and the B-phase (second phase) drive signal with a delayed phase is applied to one electrode. As described above, the drive efficiency of the ultrasonic actuator is improved by making the number of electrodes to be applied different between the A phase and the B phase.

(First Embodiment) FIGS. 8 (a) and 8 (b) show the drive characteristics of the present embodiment. The conditions and how to read the drawings are the same as the drive characteristics described in the prior art, so that the description will be omitted. In this embodiment, the drive signal with the advanced phase is input to two electrodes, and the drive signal with the delayed phase is input to only one electrode. As can be seen from FIGS. 8A and 8B, the efficiency of the first embodiment is:
Up to about 22% was obtained. When the characteristics of the conventional ultrasonic actuator and the characteristics of the ultrasonic actuator of the present embodiment are compared, it is understood that the driving efficiency of the ultrasonic actuator of the present embodiment is improved by about 40% as compared with the conventional ultrasonic actuator.

(Second Embodiment) Next, a second embodiment will be described. FIG. 4 is a block diagram illustrating a configuration of a control unit according to the second embodiment. The following description of each embodiment will be made for portions different from the above-described first embodiment, and redundant description will be omitted. The ultrasonic actuator of the present embodiment differs from the ultrasonic actuator of the first embodiment in that amplification factor setting devices 35-1 and 35-2 are provided. In the present embodiment, the phase shifter 22 is connected between the A phase and the B phase by 9
A phase difference of 0 ° (π / 2) is created. The advance / delay relationship between the A phase and the B phase is set by main controller 60 according to the moving direction of relative moving member 15. The A-phase and B-phase drive signals input from the phase shifter 22 to the amplifiers 23-1 and 23-2 are amplified according to a desired drive state. Is different. In other words, the gain setting units 35-1 and 35-2 instruct to set the gain of the drive signal whose phase is delayed among the two drive signals to be lower than the gain of the drive signal whose phase is advanced. Is issued. The amplification factor setting units 35-1 and 35-2 issue the instruction based on the optimal amplification factor data sent from the main controller 60. The optimal amplification factor depends on the conditions of the elastic body, the electromechanical transducer, and the like. However, when the amplification factor of the driving signal whose phase is advanced is 100, the amplification factor of the driving signal whose phase is delayed is 5 to 50. And the range of 20 to 40 is preferable. Amplifiers 23-1, 2
The drive signal amplified in 3-2 is applied to the electrodes 12a to 12d to excite the piezoelectric element 12.

In this embodiment, the gain setting device 35-1,
Since the gain of the drive signal in the amplifiers 23-1 and 23-2 is set by 35-2, finer adjustment is possible.

(Third Embodiment) Next, a third embodiment will be described. FIG. 5 is a block diagram illustrating a configuration of a control unit according to the present embodiment, and FIG. 2 is a diagram illustrating electrodes 12a to 12d according to the first embodiment.
FIG. 9 is a plan view showing a structure of electrodes 12a ′ to 12d ′ in the present embodiment corresponding to FIG. The ultrasonic actuator according to the present embodiment is different from the ultrasonic actuator according to the first embodiment in that the current flowing in the first embodiment is adjusted by the number of electrodes to which the drive signal is applied. In the present embodiment, the point is that the inflowing current is adjusted by reducing the area of the electrode to be applied.

The piezoelectric element 12 of this embodiment has electrodes 12a 'to 12d' as shown in FIG. The electrode 12a 'is from the partial electrodes a1 to a3, the electrode 12b' is from the partial electrodes b1 to b3, and the electrode 12c 'is the partial electrodes c1 to c.
3, the electrode 12d 'is composed of partial electrodes d1 to d3.

The partial electrodes a1 to a3, b1 to b3, c1
c3, d1 to d3 are between the respective partial electrodes, for example, a
It is a silver electrode with a narrow gap between 1 and a2,
A lead wire for applying a drive signal is soldered.
A2, b2, c2, and d2 of the partial electrodes are each 4
It is provided at the position of the antinode of the next bending vibration B4. Also,
In the electrode 12a ', the area of the combined partial electrodes a1 and a3 on both sides is substantially equal to the area of the central partial electrode a2, and the other electrodes 12b' to 12d 'also
As exemplified by the electrode 12a ', the combined area of the partial electrodes on both sides substantially coincides with the area of the central partial electrode.

Next, the control section 40 of the present embodiment will be described. The control section 40 inputs the A-phase and B-phase drive signals generated by the oscillator 21 to the phase shifter 22. The phase shifter 22 creates a phase difference of 90 ° (π / 2) between the A phase and the B phase. Note that the advance / delay relationship between the A phase and the B phase is based on the relative movement member 15
Is set by main controller 60 in accordance with the moving direction of.

The drive signal output from the phase shifter 22 is supplied to the amplifier 2
In 3-1 and 23-2, amplification is performed according to a desired driving state,
The switches 44-1 to 44-4 are entered.

The switches 44-1, 44-2, 44-3,
44-4 is an interlocking switch. That is, 1
When one switch is connected to the contact, the remaining three switches are also connected to the contact, and when one switch is connected to the contact, the remaining three switches are also connected to the contact. Has become.

When the B-phase drive signal is behind the A-phase drive signal, the switches 44-1 to 44-4
Are connected to the contacts, and when the A-phase drive signal is later than the B-phase drive signal, the switches 44-1 to 44-
4 is connected to the contact. Thus, the switch 44-1
Switching of .about.44-4 is interlocked with the phase shifter 22, and is performed by a main controller (not shown).

The A-phase and B-phase drive signals are supplied to the switch 44-
The voltage is applied to the partial electrodes selected by 1 to 44-4, and the piezoelectric element 12 is vibrated. Here, for example, switch 4
When 4-1 is connected to the contact, the partial electrode a
A drive voltage is applied to 1, a2, and a3. Since the partial electrodes a1, a2, and a3 are close to each other and the same drive signal is applied, the partial electrodes a1, a2, and a3 continue to generate vibration as one electrode. When the switch 44-1 is connected to the contact, the drive signal is applied only to the partial electrode a2, so that only the partial electrode a2 causes vibration as an electrode.

The partial electrodes a2, b2, c2, d2
Is provided at the position of the antinode of the fourth-order bending vibration B4, so that even if the area of the electrode becomes small, the vibration can be efficiently generated.

In this embodiment, the piezoelectric element 12
The driving efficiency is improved by adjusting the applied force according to the area of the portion to which the AC voltage is applied. In the present embodiment, the area of the combined partial electrodes on both sides and the area of the central partial electrode in each electrode are substantially the same, but the present invention is not limited to this, and the partial electrodes on both sides are not limited to this. The ratio of the combined area to the area of the central partial electrode can be set freely according to the ultrasonic actuator, such as 1: 2, 1: 3, 2: 1 and 3: 1.

Furthermore, in this embodiment, each electrode has three partial electrodes, but the present invention is not limited to this, and two or four or more partial electrodes may be used. The point is that the magnitude of the current can be adjusted by changing the area of each electrode. In the description of each embodiment, an example in which the actuator is an ultrasonic actuator using an ultrasonic vibration region is described. However, the invention is not limited to ultrasonic actuators,
The same applies to a vibration actuator using a vibration region other than ultrasonic waves.

In each embodiment, an example is described in which an elastic body (vibrator) having a substantially rectangular flat outer shape and generating primary longitudinal vibration and quaternary bending vibration is used. I took it. However, the present invention is not limited to this mode. For example, the third article in the document "VIBROMOTORS FOR PRECISION MICROROBOTS"
Various oscillators disclosed in Table 2.8 on page 7,
Disc-shaped, ring-shaped, rod-shaped, plate-shaped, and linear oscillators disclosed in "New Edition Ultrasonic Motor" (by Sadayuki Ueba and Yoshiro Tomikawa, published by Trikepus) The same applies to various types of transducers.

[0038]

As described above in detail, according to the present invention, the first AC power and the second AC power can be adjusted, and the vibration actuator can be driven with high driving efficiency. Therefore, when the vibration actuator is driven by the battery, the life of the battery can be extended. Further, it is more effective than the case where vibration is a combination of primary longitudinal vibration vibrating in the same direction as the relative movement direction and quaternary bending vibration vibrating in a direction substantially perpendicular to the vibration plane of the longitudinal vibration. The AC voltage can be easily adjusted by changing the number of electrodes to which the AC voltage is input.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a driving unit of a vibration actuator according to the present invention.

FIG. 2 is a schematic view illustrating an electrode according to a third embodiment.

FIG. 3 is a block diagram illustrating a configuration example of a drive circuit according to the first embodiment.

FIG. 4 is a block diagram illustrating a configuration example of a drive circuit according to a second embodiment.

FIG. 5 is a block diagram illustrating a configuration example of a drive circuit according to a third embodiment.

FIG. 6 is a block diagram illustrating a configuration example of a conventional driving circuit.

FIG. 7 is an explanatory diagram showing a conventional driving efficiency.

FIG. 8 is an explanatory diagram showing the driving efficiency of the first embodiment of the first example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Drive part 11 Elastic body 12 Piezoelectric element 12a-12d Electrode 13a, 13b Projection part 15 Relative moving member 21 Oscillator 22 Phase shifter 23-1, 23-2 Amplifier 24-1, 24-2 Switch 35-1, 35- 2 Gain setting device

Claims (4)

[Claims] An electromechanical transducer having an elastic body, a plurality of electrodes joined to the elastic body, and a second phase AC voltage having a first phase and a second phase delayed from the first phase. And a controller that applies a phase AC voltage to generate vibration in the elastic body, and drives the vibration actuator by generating relative motion between the elastic body and a relative moving member facing the elastic body. The driving device for a vibration actuator, wherein the current flowing by the first phase AC voltage and the current flowing by the second phase AC voltage are made different. 2. The vibration control apparatus according to claim 1, wherein the control unit includes a first-order longitudinal vibration that vibrates in a direction substantially the same as the direction of the relative movement and a fourth-order bending vibration that vibrates in a direction substantially perpendicular to a vibration plane of the longitudinal vibration. The driving device for a vibration actuator according to claim 1, wherein the driving device generates a vibration in which the vibration is combined. 3. The method according to claim 1, wherein the control unit adjusts the AC voltage by at least one of an area of a portion to which the AC voltage is applied and an applied voltage. . 4. An electrode to which the AC voltage is applied is four, and the AC voltage of the first phase is applied to two of the four electrodes.
4. The vibration actuator according to claim 1, wherein the second phase AC voltage is applied to one of the four electrodes. 4. Drive.