JP2001156352A - Bimorph actuator and actuator control device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bimorph actuator comprising an actuator-driving electrode and a sensor electrode. SOLUTION: A bimorph actuator 10 is provided where first and second piezoelectric plates 11 and 12 are laminated and jointed and then a voltage is applied between them for expansion/shrinkage, in different direction each other, along the lengthwise direction of the piezoelectric plates 11 and 12. Here, first and second electrodes 11e and 11d are formed on an external surface 11b of the first piezoelectric plate 11 while first and second electrodes 12c and 12d are formed on an external surface 12b of the second piezoelectric plate 12. Either a pair of first electrodes 11c and 12c formed on the first and second piezoelectric plates 11 and 12 or a pair of second electrodes 11d and 12d formed on the first and second piezoelectric plates 11 and 12 is used as the actuator-driving electrode while the remaining pair is used as a sensor electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bimorph actuator in which an actuator driving electrode and a sensor electrode are formed, and an actuator control device using the bimorph actuator.

[0002]

2. Description of the Related Art Bimorph actuators, in which first and second piezoelectric plates are bonded together via phosphor bronze, are used in various forms depending on the use, required displacement, generated force, and the like. I have.

A bimorph actuator of this type is, for example, a helical scan type video tape recorder (V
TR).

In the above-mentioned helical scan video tape recorder (VTR), a magnetic head is integrally mounted on a rotating drum which is rotatably supported coaxially with a fixed drum, and is fixed to the fixed drum and the rotating drum. On a magnetic tape wound with a predetermined inclination angle,
Recording tracks inclined according to the running speed of the magnetic tape and the rotation speed of the magnetic head are formed. However, when reproducing a magnetic signal from a recording track formed on a magnetic tape at a speed different from the recording speed such as still, slow motion, double speed or reverse mode, the magnetic head scans at a different inclination from the recording track. Therefore, the magnetic head scans off the recording track. For this reason, guard band noise and crosstalk occur, which has been a problem.

Therefore, the above-mentioned VTR is provided with an actuator control device (head actuator) for tracking so that the magnetic head can accurately scan the recording track in various variable speed modes. For example, FIG.
A conventional bimorph actuator is used in an actuator control device as shown in FIG.

FIGS. 3A and 3B are top views for explaining a conventional bimorph actuator and an actuator control apparatus using the conventional bimorph actuator.
It is a side view.

3 (a) and 3 (b), a conventional bimorph actuator 20 uses two long and substantially trapezoidal piezoelectric ceramics and the like to form first and second piezoelectric plates 21 and 22. The phosphor bronze 23 is vertically overlapped with a phosphor bronze 23 interposed therebetween and bonded with an adhesive (not shown) or the like.

Next, an actuator control device using the above-mentioned conventional bimorph actuator 20 will be described. One end of the bimorph actuator 20 is supported by a head base 24 provided on a rotating drum (not shown) in a cantilevered state. A magnetic head 25 is attached to the other end of one of the first and second piezoelectric plates 21 and 22, and the magnetic head 25 slides on a magnetic tape 26. The electrodes 21a and 22a and the phosphor bronze 2 formed on the outer surfaces of the first and second piezoelectric plates 21 and 22, respectively.
3, DC power supplies 27 and 28 are connected as shown in FIG.
Each voltage from each DC power supply 27, 28 is applied to the electrodes 21a, 22
a, for example, by applying a positive voltage (negative voltage) to the first piezoelectric plate 21 and applying a negative voltage (positive voltage) to the second piezoelectric plate 22, respectively. Board 2
One of the piezoelectric plates 21 (22) along the length direction of the first and second 22
Extend, and the other piezoelectric plate 22 (21) contracts, so that it expands and contracts in different directions, thereby causing a bending displacement in the direction of arrow A (B). Accordingly, the magnetic head 25 attached to the other end of the bimorph actuator 20 is displaced in the same direction as the arrow, so that the magnetic head 25 and the magnetic tape 26 are displaced.
, The recording / reproducing signal can be prevented from lowering due to the tracking of the magnetic head 25.

[0009]

When the relative position between the magnetic head 25 and the magnetic tape 26 is changed by using the bimorph actuator 20, the bimorph actuator 20 can take a large displacement, but the input resonance level is high. Or the magnetic head 25 is
The magnetic head 25 is shifted from a recording track on the magnetic tape 26 by receiving a load torque by sliding on the magnetic tape 26. For this purpose, in Japanese Patent Application Laid-Open No. H08-111012, although not shown, a strain gauge (strain gauge) is directly adhered to the outer surface of an electro-mechanical transducer (bimorph actuator) to perform feedback control, and resonance or the like is performed. Although an example in which the influence of the load torque is reduced is disclosed, the attachment of the strain gauge (strain gauge) causes deterioration of the linearity characteristics and hysteresis characteristics of the electro-mechanical conversion element (bimorph actuator). .

Therefore, a bimorph actuator having an actuator driving function and a sensor function integrally with only one bimorph actuator without attaching a strain gauge (strain gauge) is desired, and the function of the bimorph actuator is desired. There is a demand for an actuator control device capable of effectively controlling the actuator.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a first invention is to superimpose and join first and second piezoelectric plates to form the first and second piezoelectric plates. A bimorph actuator that expands and contracts in different directions along the length direction of the two piezoelectric plates by applying a voltage between the piezoelectric plates, wherein a first, a second, and a third piezoelectric plates are provided on the outer surface of the first piezoelectric plate.
A pair of first electrodes formed on the first and second piezoelectric plates, wherein first and second electrodes are formed on the outer surface of the second piezoelectric plate; A bimorph actuator, wherein one of the sets of the second electrodes formed on the first and second piezoelectric plates is used as an actuator driving electrode, and the other set is used as a sensor electrode. is there.

According to a second aspect of the present invention, there is provided an actuator control apparatus using the bimorph actuator according to the first aspect of the present invention, wherein the actuator driving electrode is used to expand and contract the first and second piezoelectric plates. An actuator control device comprising: a connected power supply; an amplification unit that amplifies an output from the sensor electrode; and a feedback circuit that feeds back an output from the amplification unit to the actuator driving electrode side. is there.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a bimorph actuator according to the present invention and an actuator control device using the bimorph actuator will be described below in detail with reference to FIGS.

FIGS. 1A to 1C are a top view, a side view, and a bottom view for explaining a bimorph actuator according to the present invention and an actuator control device using the bimorph actuator. FIG. FIG. 5 is a diagram illustrating a state in which an output of a sensor is fed back to an input side of actuator driving in an actuator control device using a bimorph actuator.

A bimorph actuator 10 according to the present invention shown in FIG. 1 uses two long and substantially trapezoidal piezoelectric ceramics or the like, and first and second piezoelectric plates 11 and 12.
Are overlapped vertically and joined. At this time, the bimorph actuator 10 is connected to the bonding surface 1 of the first piezoelectric plate 11.
1a and the bonding surface 12a of the second piezoelectric plate 12 are cleaned,
Hydroxyl groups are formed on the surface by a hydrophilic treatment, and the constituent atoms are directly chemically bonded to each other by heat treatment.

In the embodiment, the planar shape of the bimorph actuator 10 is formed to be substantially trapezoidal. However, the present invention is not limited to this. For example, the bimorph actuator 10 may have a rectangular shape, and the first and second piezoelectric plates 11 and 12 Any shape that can expand and contract in the length direction may be used.

Also, the bimorph actuator 10
A first electrode 11c having conductivity along an outer periphery of a substantially trapezoidal shape on an outer surface 11b (upper surface in the drawing) of the first piezoelectric plate 11
Are formed, and a second electrode 11d having conductivity is formed inside the first electrode 11c. At this time, the first electrode 11c and the second electrode 11d are electrically isolated by a slit-shaped space 11e.

Similarly to the above, a first electrode 12c having conductivity is formed on the outer surface 12b (the lower surface in the figure) of the second piezoelectric plate 12 along the outer periphery of the substantially trapezoidal shape. A second electrode 12d having conductivity is formed inside the first electrode 12c. At this time, the first electrode 12c
And the second electrode 12d are electrically isolated by a slit-shaped space 12e.

Further, the first electrodes 11c and 12c formed on the first and second piezoelectric plates 11 and 12 and the second electrode 1
1d and 12d are opposed to each other via the joint surfaces 11a and 12a, and are formed in substantially the same size and shape.

Next, an actuator control device using the bimorph actuator 10 will be described.

In this actuator control device, one end of the bimorph actuator 10 is supported in a cantilever manner on a head base 13 provided on a rotating drum (not shown), and one of the first and second piezoelectric plates 11 and 12 is provided. A magnetic head 14 is attached to the other end of one of the piezoelectric plates, and the magnetic head 14 slides on a magnetic tape 15.
Then, the second electrode 11d formed on the outer surface 11b of the first piezoelectric plate 11 and the outer surface 12 of the second piezoelectric plate 12
b, a power supply 16 is connected between the second electrode 12d and the second electrode 12d.
For example, a positive voltage (negative voltage) is applied to the first piezoelectric plate 11 while a negative voltage (positive voltage) is applied to the second piezoelectric plate 12.
Is applied to the first and second piezoelectric plates 11, 1
One piezoelectric plate 11 (12) extends along the length direction of the two, and the other piezoelectric plate 12 (11) contracts, so that it expands and contracts in different directions, thereby causing a bending displacement in the direction of arrow A (B). . Accordingly, the bimorph actuator 1
Since the magnetic head 14 attached to the other end of the magnetic head 14 is displaced in the same direction as the arrow, the relative position between the magnetic head 14 and the magnetic tape 15 is changed. You can do it. Therefore, the set of the second electrodes 11 d and 12 d formed on the first and second piezoelectric plates 11 and 12 functions as an actuator driving electrode of the bimorph actuator 10.

The first electrode 11c formed on the outer surface 11b of the first piezoelectric plate 11 and the first electrode 12c formed on the outer surface 12b of the second piezoelectric plate 12 serve as amplifying means. It is connected to an operational amplifier 17 and obtains from the operational amplifier 17 a sensor output such as a force or stress or acceleration caused by displacement (movement) of the first and second piezoelectric plates 11 and 12. Therefore, the set of the first electrodes 11 c and 12 c formed on the first and second piezoelectric plates 11 and 12 functions as a sensor electrode of the bimorph actuator 10.

In the embodiment, the first electrodes 11c, 12c
c is a sensor electrode and the second electrodes 11d and 12d are actuator driving electrodes. However, the invention is not limited to this. The first electrodes 11c and 12c are actuator driving electrodes and the second electrodes 11d and 12d are not limited thereto. May be used as a sensor electrode.

As described above, the first and second piezoelectric plates 11, 1
2 on the outer surfaces 11b, 12b.
c and the second electrodes 11d and 12d, the actuator drive function and the bimorph actuator 10
And a sensor function for detecting the movement of the actuator can be integrally provided in one bimorph actuator 10. At this time, the first electrodes 11c and 12c (or the second electrodes) serving as sensor electrodes are used instead of attaching the strain gauges (strain gauges) to the bimorph actuator 10 as described in the problem of the conventional example. Electrodes 11d, 12
Since the sensor output from d) can be used, no stress is applied to the first and second piezoelectric plates 11 and 12, the linearity characteristic and the hysteresis characteristic are less deteriorated, and the structure is simple. Parts cost is reduced.

Next, another embodiment of the actuator control device will be described with reference to FIG. The same components as those of the actuator control device shown in FIG. 1 are denoted by the same reference numerals, and different components will be denoted by new reference numerals, and only different points will be described.

In FIG. 2, first and second piezoelectric plates 11,
A first electrode (sensor electrode) 11c formed at 12;
The sensor output from 12c is input to an operational amplifier 17 and amplified, and the output from the operational amplifier 17 is passed through an adder / subtractor 18 and an operational amplifier 19 constituting a feedback circuit, and is formed on the first and second piezoelectric plates 11 and 12, respectively. (Actuator drive electrodes) 11d and 12d. Thus, the actuator drive can be feedback-controlled by the sensor output, so that the actuator drive can be reliably and accurately performed. At this time, when the magnetic head 14 is attached to one of the first and second piezoelectric plates 11 and 12,
The relative position between the tape and the magnetic tape 15 can be reliably feedback-controlled to the target recording track position.

In the above embodiment, the case where the magnetic head 14 is attached to the bimorph actuator 10 has been described. However, the present invention is not limited to this, and the bimorph actuator 10 according to the present invention can be applied to various usage forms. .

[0028]

According to the bimorph actuator of the present invention described in detail above, the actuator drive function can be achieved by simply forming the first electrode and the second electrode on the outer surfaces of the first and second piezoelectric plates, A sensor function for detecting the movement of the bimorph actuator can be integrally provided in one bimorph actuator. Further, the first electrode (or the second electrode) serving as the sensor electrode is used instead of attaching the strain gauge (strain gauge) as described in the problem of the conventional example to the bimorph actuator according to the present invention. ) Can be used, so that stress is not applied to the first and second piezoelectric plates, linearity characteristics and hysteresis characteristics are less deteriorated, and the structure is simple, so that component costs are low. become.

According to the actuator control device of the present invention, since the actuator drive can be feedback-controlled by the output of the sensor, the actuator drive can be performed reliably and accurately.

[Brief description of the drawings]

FIGS. 1A to 1C are a top view, a side view, and a bottom view for explaining a bimorph actuator according to the present invention and an actuator control device using the bimorph actuator.

FIG. 2 is a diagram showing a state in which an output of a sensor is fed back to an input side of an actuator drive in an actuator control device using a bimorph actuator according to the present invention.

3A and 3B are a top view and a side view for explaining a conventional bimorph actuator and an actuator control device using the conventional bimorph actuator.

[Explanation of symbols]

Reference numeral 10: bimorph actuator, 11: first piezoelectric plate, 11a: bonding surface, 11b: outer surface, 11c: first electrode, 11d: second electrode, 11e: interval, 12: second
, A piezoelectric plate, 12a ... joining surface, 12b ... outer surface, 12c ...
1st electrode, 12d ... 2nd electrode, 12e ... interval, 13
... head base, 14 ... magnetic head, 15 ... magnetic tape,
16 ... power supply, 17 ... amplification means (operational amplifier), 18, 1
9 feedback circuit, 18 adder / subtractor, 19 operational amplifier.

Claims (2)

[Claims] 1. A method according to claim 1, wherein said first and second piezoelectric plates are overlapped and joined to each other, and a voltage is applied between said first and second piezoelectric plates so as to be different from each other along the length direction of both piezoelectric plates. A bimorph actuator that expands and contracts, wherein first and second electrodes are formed on an outer surface of the first piezoelectric plate, and
First and second electrodes are formed on an outer surface of the second piezoelectric plate, and a pair of first electrodes formed on the first and second piezoelectric plates is combined with the first and second piezoelectric plates. A bimorph actuator, wherein one of a pair of second electrodes formed on a plate is used as an actuator driving electrode, and the other pair is used as a sensor electrode. 2. An actuator control device using a bimorph actuator according to claim 1, wherein a power supply connected to said actuator drive electrode for expanding and contracting said first and second piezoelectric plates; An actuator control device comprising: an amplifying unit that amplifies an output from an electrode; and a feedback circuit that feeds back an output from the amplifying unit to the actuator driving electrode side.