JP2004048984A - Piezoelectric actuator and electronic apparatus provided therewith - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a piezoelectric actuator that can perform non-resonating drive and whose structure is simple. <P>SOLUTION: The piezoelectric actuator 1 comprises a plurality of piezoelectric materials 1a, 1b, 1c that are displaced in different directions. Driving force can be obtained by synthesizing the displacement of these piezoelectric materials 1a, 1b, 1c. Also, the simple structure of the actuator 1 is achievable, because it could be constituted of a piezoelectric element. Furthermore, it is durable enough against destruction even if a high voltage is impressed and large displacement is obtainable even in a non-resonating state. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric actuator and an electronic device including the piezoelectric actuator, and more particularly to a piezoelectric actuator capable of performing high-accuracy positioning control.
[0002]
[Prior art]
In recent years, high positioning accuracy has been demanded for driving a stage used for a manufacturing apparatus including semiconductors, a measuring instrument or the like, or a head used for an information device such as a hard disk or a DVD.
[0003]
Electromagnetic actuators have been used for these drive units for a long time, but recently, with the demand for high-precision positioning, piezoelectric elements and ultrasonic motors using piezoelectric elements have been used ( For example, see Non-Patent Document 1.)
[0004]
[Non-patent document 1]
Koji Kosaka Development of non-resonant type ultrasonic motor drive stage and development of ultra-precision XY stage using the same Stage No. 2002-1
[0005]
[Problems to be solved by the invention]
However, the displacement obtained by using the deformation of the piezoelectric element is extremely small, so that the use thereof is limited. Also, in the case of an ultrasonic motor utilizing resonance of an elastic body, the resonance point fluctuates due to the influence of temperature, load, and the like, so that a drive circuit for stable driving is complicated. In addition, particularly in the case of a linear type ultrasonic motor, there is a problem that it is difficult to support the vibration motor without disturbing the vibration, and it is difficult to perform high-precision positioning due to variations in individual products and insufficient rigidity of the support portion. .
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the piezoelectric actuator according to the present invention is driven without using resonance of an elastic body. Therefore, by constructing the drive unit with a plurality of piezoelectric bodies displaced in different directions and integrally configuring the drive unit with a piezoelectric body, a large displacement can be obtained without using resonance, and the structure and manufacturing Make it easy.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0008]
1 and 2 show a basic configuration of a piezoelectric actuator according to the present invention.
[0009]
In FIG. 1, a piezoelectric actuator 1 serving as a driving unit includes a first piezoelectric body 1a, a second piezoelectric body 1b, and a third piezoelectric body 1c. The end faces of the second piezoelectric body 1b and the third piezoelectric body 1c are provided with friction materials 2a and 2b made of, for example, resin containing carbon fiber or ceramics such as alumina or zirconia.
[0010]
A pressing force is applied to the piezoelectric actuator 1, and the piezoelectric actuator 1 is provided on, for example, rollers 3a and 3b, and is in contact with a rail 4 which is a driven portion that operates linearly.
[0011]
Since the first piezoelectric member 1a, the second piezoelectric member 1b, and the third piezoelectric member 1c are displaced in different directions, the displacement of the friction member 2 is added to the driven portion by combining these displacements. A displacement having both a displacement component x in the driving direction and a displacement component y in the contact pressure direction between the driving unit and the driven unit, for example, an elliptical motion can be generated. Therefore, the rail 4 can be moved.
[0012]
Conversely, if the rail 4 is fixed and the piezoelectric actuator 1 is free to move in one direction, the piezoelectric actuator 1 itself can be driven.
[0013]
In FIG. 2, a piezoelectric actuator 5 serving as a driving unit includes a first piezoelectric body 5a, a second piezoelectric body 5b, and a fixing member 8.
[0014]
A pressing force is applied to the fixing member 8 provided at one end of the first piezoelectric body 5a, and a rotational force is applied to the piezoelectric actuator 5 about the rotating shaft 8a, so that one end of the second piezoelectric body 5b is driven. The portion 6 is in contact with the rotor 6a.
[0015]
Since the first piezoelectric body 5a and the second piezoelectric body 5b are displaced in different directions, the displacement of the driven part in the driving direction of the driven portion is added to the tip of the second piezoelectric body 5b by combining these displacements. Since a displacement having both x and a displacement component y in the contact pressure direction between the driving unit and the driven unit, for example, an elliptical motion can be generated, the rotor 6a can be rotated.
[0016]
Therefore, if the rotor 6a is provided with the arm 6b and the head 6c is provided at the tip of the arm 6b, for example, information on the magnetic disk 7 can be read. The piezoelectric actuator of the present invention has high responsiveness, high rigidity, and high precision positioning accuracy, so that it is possible to increase the track density of the disk, and it is possible to read information from a small, high-density disk. is there. Further, power consumption is small, and power saving of the device can be achieved.
[0017]
Further, the piezoelectric actuator 5 can be easily applied to a linear actuator as described above.
[0018]
By the way, if only the first piezoelectric element 5a is driven here, the driven part which comes into pressure contact with the first piezoelectric element 5a can be operated with the movement. Since the piezoelectric body and the driven portion are always in contact with each other and the slight displacement of the piezoelectric element can be directly used, a minute displacement operation can be performed with good responsiveness.
[0019]
This operation is used for, for example, a fine adjustment operation of a pickup in an information recording device. By combining this operation with the above-described normal operation, high-precision positioning can be performed, and the pickup operation can instantaneously cope with uneven rotation and eccentricity of the disk.
[0020]
Note that this fine movement method is not limited to the piezoelectric actuator of the present invention, but may be applied to any piezoelectric actuator having a piezoelectric body that is independently displaced in two directions.
[0021]
(Embodiment 1)
The configuration and driving method of the piezoelectric actuator 9 of the present invention will be described with reference to FIGS.
[0022]
The piezoelectric actuator 9 includes a first piezoelectric body 9a, a second piezoelectric body 9b, and a third piezoelectric body 9c. Each of the piezoelectric bodies 9a, 9b, 9c generates a displacement in the longitudinal direction. The piezoelectric actuator 9 may be constituted by one piezoelectric body, or may be constituted by joining a plurality of piezoelectric bodies such as a laminated actuator. A voltage may be applied in the polarization direction and a piezoelectric longitudinal effect using distortion in the polarization direction may be used, or a voltage may be applied in the polarization direction and a piezoelectric transverse effect using distortion in a direction perpendicular to the polarization direction may be used. .
[0023]
Next, an example of a driving method will be described. In FIG. 3, the third piezoelectric body 9c is extended, and the second piezoelectric body 9b is set to a reference position (in a state where no voltage is applied) or contracted ((1)). The first piezoelectric member 9a is extended from the state (1) (2). The second piezoelectric body is extended from the state of (2) (3). From the state of (3), the third piezoelectric body 9c is set to the reference position (voltage applied state) or contracted ((4)). From the state of (4), the first piezoelectric body 9a is set to the reference position (voltage applied state) or contracted ((5)). By repeating the series of steps (1) to (5), the operated object moves in a continuous operation.
[0024]
The signal applied to the piezoelectric body may be an ordinary alternating voltage having a different polarity, but it is desirable to have the same polarity as the voltage at the time of polarization. Thereby, it is not necessary to worry about the deterioration of polarization which is a concern when a voltage of the opposite polarity is applied, and a large voltage can be applied, so that a large amplitude can be obtained even in a non-resonant state.
[0025]
Here, the frequency of the signal applied to each piezoelectric body is a frequency outside the resonance of the driving unit. In particular, the frequency is lower than the first resonance point excited by applying a signal to each piezoelectric body. However, if the y-direction vibration of the piezoelectric actuator 9, that is, the vibration frequency in the direction of the contact pressure with the rail 4, is too low, the piezoelectric actuator 9 and the rail 4 are almost in contact with each other, making it impossible to operate or extremely reducing the efficiency. So there is a limit.
[0026]
FIG. 3B shows a timing example of a signal application method in each piezoelectric body, and FIG. 3C shows the movement of the free end of the piezoelectric body 9b at this time. In this way, in one cycle of the vibration displacement at the contact point of the piezoelectric body with the moving body, the displacement in the moving direction of the moving body or the piezoelectric body and the displacement in the contact direction of the moving body and the piezoelectric body are generated alternately. As a result, an efficient piezoelectric actuator having a long life and no slippage between the piezoelectric body and the moving body can be realized. It should be noted that such a driving method is not limited to the present piezoelectric actuator, and any other method may be used as long as such an actuator can generate displacement in these two directions. Further, the time of each state and the phase relationship of each signal are not limited to those shown here.
[0027]
As another example, in FIG. 4, the first piezoelectric member 9a is extended, the third piezoelectric member 9c is extended, and the second piezoelectric member 9b is set to a reference position (in a state where no voltage is applied) or contracted (▲ 1). ▼). The second piezoelectric element 9b is extended from the state (1), and the third piezoelectric element 9c is set to the reference position (no voltage applied) or contracted ((2)). From the state of (2), the first piezoelectric body 9a is set to the reference position (voltage applied state) or contracted ((3)). From the state of (3), the second piezoelectric body 9b is set to the reference position (voltage applied state) or contracted, and the third piezoelectric body 9c is extended ((4)). By repeating the series of steps (1) to (4), the operated object moves in a continuous operation.
[0028]
FIG. 4B and FIG. 4C show a timing example and a vibration displacement of a signal application method in each piezoelectric body, but the time of each state and the phase relationship of each signal are not limited to those shown here. . That is, the point of contact of the piezoelectric actuator 9 with the driven portion has both x and y components, and may be any as long as the moving portion can be moved. Of course, the reverse operation can be performed by changing the phase of each signal.
[0029]
The same applies to the case where the piezoelectric actuator is composed of only the first piezoelectric body and the second piezoelectric body as shown in FIG. In FIG. 2, a second piezoelectric body 5b is provided at one end of the first piezoelectric body 5a in a direction orthogonal to the displacement direction of the first piezoelectric body 5a, and a fixing member is provided at the other end of the first piezoelectric body 5a. The fixing member is supported and pressed.
[0030]
(Embodiment 2)
An example of the piezoelectric actuator of the present invention will be described with reference to FIGS. In the present embodiment, a bending displacement is used in addition to the extension displacement described above.
[0031]
In FIG. 5, a piezoelectric actuator 10 includes a piezoelectric body 10a that generates a bending displacement in a bimorph or unimorph configuration, and a second piezoelectric body 10b and a third piezoelectric body 10c that generate elongational displacement at both ends. As described above, by changing the timing of the signal applied to each of the piezoelectric bodies 10a, 10b, and 10c, it is possible to drive the driven part with the tip of the second piezoelectric body 10b and the third piezoelectric body 10c. It becomes. In addition, the second piezoelectric body 10b and the third piezoelectric body 10c may have a bimorph or unimorph configuration, and may generate a bending displacement. The bending displacement has a smaller force but provides a larger displacement, and is suitable for light load and high-speed driving.
[0032]
FIG. 6 uses only the bending displacement as described above, and the piezoelectric actuator 11 is composed of two bimorph or unimorph piezoelectric members 11a and 11b that generate a bending displacement.
[0033]
In addition, it is easy to apply shear deformation of the piezoelectric element.
[0034]
Further, as shown in FIG. 10, the driving section may be constituted by a single bimorph or unimorph piezoelectric body 18 having one end fixed. In this case, the free ends 18c and 18d of the piezoelectric body 18 perform an elliptical motion even when signals having different phases, for example, signals having different phases by 90 degrees are applied to the two piezoelectric bodies 18a and 18b constituting the piezoelectric body 15 having the bimorph structure. Therefore, it is possible to operate a driven portion or a driving portion 15 (not shown) in contact with the driving portion.
[0035]
(Embodiment 3)
An example of the actuator of the present invention including a manufacturing method will be described.
[0036]
FIG. 7A is a view showing the appearance of the piezoelectric actuator 12 of the present invention, in which a first piezoelectric body 12i, a second piezoelectric body 12j, and a third piezoelectric body 12k are integrally formed, and Friction members 13a and 13b are joined to the tips of the piezoelectric body 12j and the third piezoelectric body 12k. The first piezoelectric body 12i is displaced in the x direction, and the second piezoelectric body 12j and the third piezoelectric body 12k are displaced in the y direction.
[0037]
Hereinafter, the manufacturing method will be described. As shown in FIG. 7 (c), electrodes 14a, 14b and 14c are provided on the upper surface of the sheet 12c made of a piezoelectric material. As shown in FIG. 7D, an electrode 14d is provided on the upper surface of a sheet 12d made of a piezoelectric material. After alternately stacking and calcining a plurality of sheets 12c and 12d before firing, grooves 12a and 12b are provided by dicing or the like. After that, main firing is performed. Actually, a plurality of piezoelectric actuators can be manufactured at once by stacking one large sheet including a plurality of sheets 12c and 12d and then cutting into individual piezoelectric actuators.
[0038]
FIG. 7B shows the side surface of the piezoelectric actuator 12, and the electrodes 14a, 14b, 14c, and 14d are short-circuited by the side electrodes 14f, 14g, 14h, and 14e, respectively. By applying a high electric field to the electrodes 14f, 14g, and 14h while using the electrode 14e as GND, each sheet is polarized in its thickness direction. The portion sandwiched between the electrodes 14a and 14d is displaced as the first piezoelectric body 12i, the portion sandwiched between the electrodes 14b and 14d is displaced as the second piezoelectric material 12j, and the portion sandwiched between the electrodes 14c and 14d is The third piezoelectric element 12k is displaced.
[0039]
Here, the electrodes are short-circuited on the side surface of the piezoelectric actuator 12, but a through hole or the like may be used.
[0040]
FIG. 8 shows a modification of the electrode shown in FIG. The electrode 14a in FIG. 7 is divided into the electrodes 14i and 14j in FIG. By providing a portion without an electrode at the center of the piezoelectric body 12e, the center of the first piezoelectric body 12i is not displaced, so that it is not affected by pressure or support.
[0041]
As described above, since the piezoelectric actuator can be driven at a low voltage by being constituted by the laminated elements, the driving circuit is simplified. In addition, since it is integrally formed without a joint, it is strong against destruction, and a large voltage can be applied, so that a large displacement can be obtained. Further, since the structure is simple and the manufacturing is easy, an inexpensive piezoelectric actuator can be realized.
[0042]
By the way, various examples can be considered for the stacking direction. FIG. 9 shows an example of the configuration of the piezoelectric actuator of FIG. 2, which is stacked in the width direction (dotted lines in the figure indicate boundaries between layers). In this case, the first piezoelectric material uses the piezoelectric lateral effect, and the second piezoelectric body uses the piezoelectric longitudinal effect. Since the piezoelectric longitudinal effect has a high electromechanical coupling coefficient and a large displacement and force can be obtained, in the present configuration, the pressing force can be increased, so that a large torque can be obtained. In addition, if the length of the first piezoelectric material is increased or the piezoelectric longitudinal effect is used, a displacement in the thrust direction can be obtained, so that a large propulsion speed can be obtained.
[0043]
In this way, the degree of freedom in designing according to the application and specifications is high.
[0044]
【The invention's effect】
As described above, according to the present invention, it is possible to realize an inexpensive piezoelectric actuator capable of highly accurate positioning with a simple structure. In particular, the present piezoelectric actuator has a high degree of freedom in shape, and all or almost all of the piezoelectric actuator including the supporting portion and the pressing portion of the piezoelectric actuator can be constituted by only the piezoelectric element, so that the size and thickness can be reduced. . By mounting the piezoelectric actuator in an electronic device, it is possible to improve the performance of the electronic device, such as miniaturization, low power consumption, and vibration resistance.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a piezoelectric actuator of the present invention.
FIG. 2 is a diagram showing a piezoelectric actuator of the present invention and an application example thereof.
FIG. 3 is a diagram illustrating a driving principle of the piezoelectric actuator of the present invention.
FIG. 4 is a diagram illustrating another driving principle of the piezoelectric actuator of the present invention.
FIG. 5 is a diagram showing an example in which bending displacement is used in the piezoelectric actuator of the present invention.
FIG. 6 is a diagram showing another example using a bending displacement in the piezoelectric actuator of the present invention.
FIG. 7 is a diagram showing a configuration and a manufacturing method of the piezoelectric actuator of the present invention.
FIG. 8 is a view showing another example of the electrode pattern of the piezoelectric actuator of the present invention.
FIG. 9 is a view showing another example of the piezoelectric actuator of the present invention in which the laminating directions are different.
FIG. 10 is a diagram showing another configuration of the piezoelectric actuator of the present invention.
[Explanation of symbols]
1,5,9,10,11,12,15,18 Piezoelectric actuators 4,6 Actuator 8,17 Fixing member

Claims (10)

A first piezoelectric body supported at one end and moving in a first direction,
A second piezoelectric body, which is provided with one end in contact with the other end of the first piezoelectric body and in a direction orthogonal to the direction of displacement of the first piezoelectric body, and moves in a direction different from the first direction Having a drive unit consisting of
A piezoelectric actuator in which the other end of the second piezoelectric body of the drive section contacts a driven section. A first piezoelectric body that moves in a first direction;
One end has a drive unit consisting of a second piezoelectric body and a third piezoelectric body that move in a direction different from the first direction in contact with the first piezoelectric body,
A piezoelectric actuator in which the other end of the second piezoelectric body or the third piezoelectric body of the drive section contacts the driven section. The piezoelectric actuator according to claim 1, wherein the driving unit includes one piezoelectric body. The piezoelectric actuator according to claim 5, wherein the piezoelectric body is a laminated element. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator supports the first piezoelectric member or a member joined to the first piezoelectric member. The contact pressure between the drive unit and the driven unit is obtained by applying a force to the first piezoelectric body or a member bonded to the first piezoelectric body. Piezoelectric actuator. A driving unit including a first piezoelectric body that moves in a first direction and a second piezoelectric body that has one end in contact with the first piezoelectric body and moves in a direction different from the first direction. In a piezoelectric actuator in which a driven part in contact with the other end of the second piezoelectric body of the driving part or the driving part is operated by the movement of the driving part,
A piezoelectric actuator in which the drive section or the driven section is operated only by displacement of the first piezoelectric body. A driving method of a piezoelectric actuator that operates a driven part or the driving part itself, which is in contact with the driving part, by a vibration of a driving part including a piezoelectric element,
A driving method for a piezoelectric actuator, wherein a driving signal having the same polarity as the polarity of the voltage at the time of polarization of the piezoelectric element is applied. A driving method of a piezoelectric actuator that operates a driven part or the driving part itself, which is in contact with the driving part, by a vibration of a driving part including a piezoelectric element,
One cycle of the displacement of the contact point of the piezoelectric actuator with the driven part is alternately the displacement of the driving part or the driven part in the operating direction and the displacement of the driving part and the driven part in the contact direction. A driving method of a piezoelectric actuator for applying a driving signal so as to be repeated. An electronic device comprising the piezoelectric actuator according to claim 1.

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