JPH06112547A - Bending displacement actuator - Google Patents

Abstract

(57) [Abstract] [Purpose] In the case of the cantilever type, it is possible to prevent the displacement in the element longitudinal direction during bending deformation, and in the case of the double-supported beam type, the displacement in the element longitudinal direction is not constrained. An object of the present invention is to provide a bending displacement actuator that can secure a sufficient amount of displacement in the vertical direction, can correct a decrease in linearity, and can bring out the original performance of the actuator. [Structure] A bending displacement element 1 which is formed to have a constant length and is displaced in a direction perpendicular to a longitudinal direction based on an applied driving force.
In addition, the element 1 has the displacement absorbing portion K that absorbs the displacement in the longitudinal direction caused by the application of the driving force. As a result, when applied to a bending displacement actuator that controls a precise and minute displacement amount, the device itself is provided with the displacement of the drive target, the displacement amount, and the linearity reduction that occur in the longitudinal direction when the bending displacement element is bent. It becomes possible to prevent it by the displacement absorbing part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bending displacement actuator applied to a device such as a scanning tunneling microscope (STM) or a stepper that requires precise and minute control of displacement amount.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of electronic parts such as LSIs, it has been required to control the processing devices, analysis devices such as STMs and the like in units of angstroms. For fine driving of such a device, a bending displacement actuator having a bending displacement element, which is formed to have a constant length and is displaced in a direction perpendicular to the longitudinal direction based on a driving force applied, is used, for example, a piezoelectric actuator. Often.

Piezoelectric actuators are used in various forms depending on the specifications of the application, the required displacement amount, the generated force, etc. They are roughly classified into two types: laminated type and bending displacement type (bimorph type). To be done. The bending displacement type is inferior to the laminated type in the generated force in the same element size, but has an advantage that a large displacement amount can be obtained.

FIG. 19 shows a conventional example of a cantilever type bimorph type piezoelectric actuator for driving a bending displacement element in the S mode. This actuator has a structure in which one end of a bending displacement element 1 is supported by a fixing member 2, and a pair of bending displacement portions 1a and 1b made of a piezoelectric plate are bonded to each other with their expansion and contraction directions when voltage is applied reversed. It becomes. The electrode G on the joint surface is shared, and the surface side is divided into an electrode A and an electrode B (in the figure, the surface electrodes A and B are drawn apart from the bending displacement element 1 for easy understanding). The area of the electrode A on the fixed end side is set to be bent so as to be convex downward in the figure, and the area of the electrode B on the free end side is set to be bent to be convex upward in the figure. I am doing it. The bending displacement element 1
The driven object 3 is attached to the free end side of the.

At first, as shown by a broken line in FIG. 20, a true length state is obtained, but when a positive electric field is applied, as shown by a solid line in the figure, the bending displacement portions 1a and 1b are freely deformed. It bends into an S shape with the end side popping up. If a negative electric field is applied later, the original state shown by the broken line is restored.

By the way, in such a conventional actuator, since only one end of the bending displacement element 1 is fixed and the other end to which the driven object 3 is attached is free, the displacement of the bending displacement element 1 is perpendicular to the longitudinal direction of the element by driving the element. Although there is an advantage that the amount D0 can be made large, there is a drawback that the amount D0 is slightly shifted in the longitudinal direction of the element.

For example, when FIG. 20 is used for VTR tracking control, the magnetic head 3 provided at the tip of the bending displacement element 1 may be separated from the tape surface due to the contraction d in the longitudinal direction.

FIGS. 21 and 22 show a structure in which two S-mode bending displacement elements 1 are connected in the longitudinal direction, that is, an example of driving the double S-mode bending displacement element 1 for displacing the central portion of the element. There is.

FIG. 21 shows a cantilever type structure in which one end of the bending displacement element 1 is supported by a fixing member. When moving this cantilever type actuator, as shown in the figure,
When a positive electric field is applied, the central portion of the bending displacement element 1 is bent so as to be convex upward, and the displacement amount D0 is obtained in the direction orthogonal to the longitudinal direction according to the bending. In this case, the free end of the element moves in the longitudinal direction so as to contract by d in the same manner as described above.

FIG. 22 shows a double-supported beam type structure for fixing both ends of the element. When this is moved, the double-supported beam type can take a larger force against displacement than the cantilever type,
There is a merit that it can be driven at a high speed, and since both ends of the element are fixed, there is no deviation in the longitudinal direction of the element at the displacement point. However, at the time of bending, the amount of movement of d in FIG. 21 does not remain, and the tension T that tries to return the bending displacement element to the original works, and this tension suppresses the displacement amount. As a result, the original displacement amount D0 cannot be obtained, and the displacement amount decreases dD. As the amount of displacement increases, the amount of decrease dD also increases, and thus the linearity of the amount of displacement also deteriorates. FIG. 23 shows the influence data on the displacement amount by the tension T in the both-end fixed bending displacement element. When the tension does not work, the linearity is good like the straight line A ′, but when the tension works, the curve Displacement occurs as in B ', and linearity deteriorates.

[0011]

In a bending displacement actuator that obtains displacement in a direction perpendicular to the element longitudinal direction, the cantilever beam type causes a slight displacement in the element longitudinal direction during bending deformation. In the formula, since the displacement in the longitudinal direction of the element is restricted, there is a problem that the amount of displacement in the vertical direction decreases.

The present invention has been made in view of such circumstances, and in the case of the cantilever type, it is possible to prevent the displacement in the longitudinal direction of the element at the time of bending deformation, and in the case of the double-supported beam type. It is an object of the present invention to provide a bending displacement actuator capable of ensuring a sufficient amount of displacement in the vertical direction without restraining displacement in the element longitudinal direction, compensating for a decrease in linearity, and drawing out the original performance of the actuator. To do.

[0013]

To achieve the above object, the bending displacement actuator of the present invention is formed to have a constant length and is displaced in a direction perpendicular to the longitudinal direction based on a driving force applied thereto. And a displacement absorbing portion that absorbs a displacement in the longitudinal direction caused by the application of the driving force.

In the present invention, the displacement absorbing portion is provided, for example, at the central portion of the bending displacement element itself, at both ends, or at any other position as a portion that extends corresponding to the magnitude of the bending displacement. As a result, it is possible to prevent the displacement in the longitudinal direction when the element is driven or the decrease in the displacement amount due to the tension generated in the element longitudinal direction.

[0015]

According to the present invention, since the element for correcting the deviation is provided in the element itself, for example, the element for contracting the deviation extends in the longitudinal direction as much as the element contracts in the longitudinal direction when the element is bent.

Therefore, when the cantilever type is used, there is no displacement in the longitudinal direction of the element to be driven.

Further, when the double-supported beam type is used, since no tension is generated in the longitudinal direction of the element, the restraining force does not act on the bending, the displacement amount is not reduced, and the linearity is not deteriorated.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. For ease of explanation, the same reference numerals are used for the components of the embodiment corresponding to the conventional example, the components common to the embodiments, and the like.

(Embodiment 1) FIGS. 1 to 3 The present embodiment relates to a cantilever type piezoelectric displacement actuator, in which a bending displacement element is driven in S mode. That is, as shown in FIG. 1, two piezoelectric plates 1
a and 1b are attached to each other with their bending directions reversed, and one end of this bending displacement element 1 is supported by the fixing member 2 and the other end is a free end. The electrode G on the joint surface is shared, and the front surface side is divided into an electrode A and an electrode B.

The area of the electrode A on the fixed end side is set to be bent so as to be convex downward in the figure, and the area of the electrode B on the free end side is bent upward to be convex in the figure. Is set. A drive target 3 is attached to the free end side of the bending displacement element 1.

In this embodiment, in this embodiment, an extension portion K is provided between the fixed portion 2 of the bending displacement element 1 and the bending deformation portion as a displacement absorbing portion for correcting the displacement in the element longitudinal direction. The extension portion K is configured to be displaced in the thickness direction by the piezoelectric effect, and for example, is contracted in the thickness direction by applying a positive electric field and thereby extended in the longitudinal direction. An electrode C is arranged on the extension K to apply an electric field.

FIG. 2 shows the state of correction of the dent during driving. The bending displacement portions of the electrodes A and B are bent in the opposite directions with respect to the drive voltage, and the conventional S-mode bending displacement is the displacement in the direction perpendicular to the element longitudinal direction with the angle of the element tip kept parallel. Same as element, but bending displacement element 1
The extended portion K near the fixed end contracts in the thickness direction by the piezoelectric effect when a drive voltage is applied and extends in the element longitudinal direction. The amount of shrinkage in the longitudinal direction that occurs at the bending displacement portion (see d in FIG. 20)
If the amount of expansion is corrected so as to correct, the drive target 3 of the bending displacement element 1 is driven only in the direction perpendicular to the element.

FIG. 3 shows an example of the drive voltage waveform, and shows an example of the drive voltage waveform when the bending displacement element 1 is vibrated and deformed vertically from the neutral position shown by the broken line in FIG.
The sinusoidal voltage V _AG may be applied to the electrodes A and B of the bending displacement portion to change the polarity of the voltage, but the electrode C of the extension portion K
However, if the same sine wave voltage is applied, the extension K contracts with a reverse polarity voltage, which causes a problem. Therefore, the voltage V _CD that is the absolute value of the drive voltage V _AG must be applied to the electrode C. This may be supplied by a separate power source, but the drive voltage V
It can also be made from a full-wave rectifier circuit composed of _AG and a diode bridge. It goes without saying that the drive voltages that do not change the polarity can be driven by the same drive voltage.

(Embodiment 2) FIGS. 4 and 5 The present embodiment relates to a double-supported beam type piezoelectric displacement actuator, in which the bending displacement element is driven in the double S mode. That is, as shown in FIG. 4, in the both-end supported beam type, the extended portion K for correcting the displacement in the element longitudinal direction and the driving electrode C are arranged at both ends of the bending displacement element 1.

FIG. 5 shows a bending displacement element 1 as an example during driving.
Shows a state in which a drive voltage is applied so that the pixel has an upward convex state. The extending portions K near the both ends of the element extend in the element longitudinal direction, correct the deviation in the element longitudinal direction, and perform the bending operation without impairing the displacement amount of the element central portion.

The extension portion K near the both ends of the element is extended by the same amount as the contraction in the longitudinal direction caused by the bending of the central portion of the element (see d in FIG. 21), thereby generating the tension T for suppressing the displacement amount in the element. The bending displacement element can be driven without causing the bending displacement element.

(Third Embodiment) FIG. 6 This embodiment is substantially the same as the second embodiment except that an extension portion K for correcting the displacement of the bending displacement element 1 in the longitudinal direction is provided in the central portion of the element. is there. With such a configuration, the same effect as that of the above-described embodiment can be obtained.

As described above, the same result as described above can be obtained even if the bending displacement element 1 is set at the center of the element or at an arbitrary position depending on the usage condition.

(Embodiment 4) FIGS. 7 and 8 This embodiment shows a specific example of the direction of the electric field with respect to the polarization direction of the bending displacement element 1 having the above-mentioned extending portion K. In the bimorph type bending displacement element, generally, two piezoelectric plates are bonded by sandwiching a metal shim material, and FIG. 7 shows an example in which the polarization directions of the piezoelectric plates 1a and 1b are bonded in the same direction. Shown (the arrow on the element column indicates the polarization direction).

When the bending displacement element 1 is bent upwardly in a convex shape, a positive voltage is applied to the V _A terminal for driving the bending deformation portion with respect to the common GND made of the shim material, and a negative voltage is applied to the V _B terminal, and both ends are applied. A positive voltage is applied to the V _C terminal for driving the extension section provided in the above and a negative voltage is applied to the V _D terminal.

When the lens is bent downward,
_A voltage having the opposite polarity to that used when an upward convex bend is obtained is applied to the terminals V _A and V _B of the bend deforming portion.

FIG. 8 shows the relationship between the voltages applied to the terminals when the bending displacement element 1 of FIG. 7 is driven by a triangular wave, with the horizontal axis representing time.

(Embodiment 5) FIG. 9 This embodiment is an example in which two piezoelectric plates 1a and 1b are bonded with their polarization directions opposed to each other. The same voltage can be applied to the electrodes of the extension portions K of the piezoelectric plates 1a and 1b, and the V _D terminal is unnecessary.

The polarities of the voltages applied to the terminals 1a and 1b are the same as those in FIG. 7, and the time charts of the voltages when driving with a triangular wave are V _A , V _B and V _{C in} FIG.

Normally, the polarization directions of the two piezoelectric plates constituting the bimorph are the same in one plate, but the polarization directions can be changed. Polarization is formed by applying a high electric field between opposing electrodes, and the direction is determined by the polarity of the polarization electric field. It is also possible to reverse the polarization direction by 180 degrees by applying a high electric field in the direction opposite to that when the polarization is formed.

(Embodiment 6) FIG. 10 Since the bending deflection element of the present invention divides the electrodes, by selecting the polarity of the polarization electric field for each electrode region,
The polarization direction can be different. As an example thereof, FIG. 10 shows a bending displacement element 1 having a simplified wiring.

When the polarization directions under the respective electrodes of the two piezoelectric plates 1a and 1b are formed as shown by the arrows in the figure and bonded, all the surface electrodes of the bent portion can be commonly connected and the voltage terminal for bending driving is V. _A can be one.

If the bending drive terminal V _A is driven by only a positive voltage, V _C can be commonly connected to V _A ,
One-terminal drive is also possible.

(Embodiment 7) FIGS. 11 and 12 This embodiment is an example in which only the bending displacement element surface electrode is used without using the electrode positioned at the bonded portion of the bending displacement element 1. The polarization direction is changed as shown in FIG. 10 only under the electrodes on both ends of one piezoelectric plate to form the bending displacement element 1 as shown in FIG.

Part of the divided electrodes on the element surface is connected to the GND terminal, and the electrode facing the GND electrode is connected to VA and VC.

Even with such a configuration, the number of wires can be omitted as in the case of FIG.

FIG. 12 shows a method of manufacturing the bending displacement element 1 having the structure shown in FIG. As shown in FIG.
The two piezoelectric plates 1a and 1b whose polarization directions are aligned in advance are processed into a shape that can be fitted, and then bonded as shown in FIG. 12 (b).

(Embodiment 8) FIGS. 13 to 16 Piezoelectric single crystals of lithium niobate (LiNbO ₃ ) and lithium tantalate (LiTaO ₃ ) were heat-treated to have a thickness half that of the polarization inversion layer single crystal corresponding to the polarization axis. It is known to be formed up to. For example, LiNb with polarization
When a 140 ° Y-plate 1 made of an O ₃ single crystal is heat-treated at a temperature of 1050 to 1200 ° C. for 0 to 20 hours, a single crystal flat plate having a polarization inversion layer is formed. When electrodes are formed on both surfaces of the piezoelectric plate facing each other in the polarization direction and an electric field is applied in the thickness direction, the piezoelectric plate becomes a bending displacement element. The same applies to other than the 140-degree Y plate.

Therefore, in this embodiment, piezoelectric single crystal LiN is used.
In bO ₃ or LiTaO ₃ , a layer whose polarization is inverted to half the thickness by heat treatment is selectively formed, that is, an inversion layer portion that contributes to bending displacement and a non-inversion portion that contributes to tension relaxation are formed separately in one piezoelectric element. Utilizing the fact that it is possible, a means for arranging the extension portion K, which is the displacement absorbing portion for relaxing the tension, on the element itself.

That is, FIG. 13 shows a structure in which extension portions K extending in the longitudinal direction when a voltage is applied are provided at both ends of the bending displacement element 1. The regions of the electrodes A and B are bent portions in which the domain inversion layer is formed and which are deformed by the double S mode,
The both end portions forming the are the extended portions K. The polarization inversion layer L is not formed at the both ends, and the polarization directions are aligned in the thickness direction. A voltage is applied to the electrode C of the extending portion K so as to extend according to the deformation of the bent portion.

FIG. 14 shows a deformed state when driven by the double-supported beam type. Since the extending portion K extends in response to the bending of the bending displacement element 1, no tension is generated when the element is driven, and a decrease in displacement amount can be prevented.

When the bending displacement element 1 is driven by a sine wave, the displacement end is vertically deformed, but the same sine wave as the bending drive voltage cannot be applied to the extension K. If the polarity of the voltage with respect to the polarization direction of the extension portion is reversed, the extension portion K contracts, which becomes a problem. Therefore, the drive voltage V K of the extension _K has a waveform as shown in FIG. 15 with respect to the bending drive voltage VA.

A method of manufacturing the bending displacement element 1 will be described with reference to FIG. LiNbO ₃ and LiTaO ₃ can be heat-treated to form a layer whose polarization axis is inverted up to half the thickness. The piezoelectric single crystal is previously processed into a shape as shown in FIG. 16A, and then heat treatment is performed. At this time,
Processing is performed so that the thickness t1 of the thick portion of the sample is at least twice as large as the thickness t2 of the thin portion, that is, t1 ≧ 2 × t2.

By subjecting this single crystal to a heat treatment at a temperature of 1050 to 1200 ° C. for 0 to 20 hours, a domain-inverted layer is formed to half the thickness of each portion of the single crystal, and FIG.
The single crystal has a polarization distribution as shown in.

The large-thickness portion is aligned with the small-thickness portion and cut off to have a layer in which the polarization is inverted only in the central portion as shown in FIG. 16C, and both end portions have a single domain. A single crystal element as it is can be obtained.

By disposing electrodes on this, the bending displacement element 1 shown in FIG. 13 is completed. The boundary layer F of the domain-inverted layer L does not become uniformly half the thickness in the vicinity of both ends of the single crystal and the portions having different thicknesses, but it becomes complicated, but for the sake of simplicity, it is schematically shown in FIG. Note.

The bending displacement element of the present invention is the above L
The material is not limited to iNbO ₃ and LiTaO ₃ , and it goes without saying that other materials can be applied as long as the polarization distribution can be partially controlled as described above.

(Embodiment 9) FIGS. 17 and 18 This embodiment relates to an actual application example of the bending displacement element 1 having each of the above-mentioned configurations. 17 and 18 show an example applied to a fine movement XY stage used in, for example, STM (the same applies to a tracking control element of a VTR head).

In this XY stage, as shown in FIG. 17, three double-supported beam bending displacement elements 1 are combined, and two bending displacement elements 1 which are displaced in the X direction are arranged in parallel. A bending displacement element 1 ′ that is displaced in the Y direction is fixed at both ends to the center of each bending displacement element 1 with fixing members 2.
It has a shape configuration. Then, as shown in FIG. 18, the drive target 3 fixed to the central portion of the bending displacement element 1 ′ that is displaced in the Y direction is finely moved in the XY two-dimensional manner.

According to this embodiment, even if the bending displacement element 1'is largely displaced, the displacement amount at the displacement end of the central portion of the element is suppressed by the structure having the displacement absorbing portion shown in each of the above embodiments. Can be driven without

(Other Embodiments) The present invention is not limited to the above embodiments. According to the gist of the present invention, the application target is not limited to the piezoelectric body, but other ceramics, metals,
Of course, it can be applied when the plastics and their composites are applied to the bending displacement element. Other,
Various modifications can be implemented without departing from the scope of the present invention.

[0057]

As described above, according to the present invention, when applied to a bending displacement actuator for controlling a precise and minute displacement amount, a displacement or displacement of a driving object which occurs in the longitudinal direction when the bending displacement element is bent. It is possible to prevent the decrease in the amount and linearity by the displacement absorbing part provided in the element itself, and by doing so, correct the deviation in the element longitudinal direction, and the excellent effect that the element's original precision, displacement amount, and linearity can be exhibited. Played.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a view showing an operation of the same embodiment.

FIG. 3 is a diagram showing a driving method of the embodiment.

FIG. 4 is a diagram showing a configuration of a second embodiment of the present invention.

FIG. 5 is a view showing the operation of the same embodiment.

FIG. 6 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 7 is a diagram showing a configuration of a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a driving method of the embodiment.

FIG. 9 is a diagram showing a configuration of a fifth embodiment of the present invention.

FIG. 10 is a diagram showing a configuration of a sixth embodiment of the present invention.

FIG. 11 is a diagram showing a configuration of a seventh embodiment of the present invention.

12A and 12B are views showing the manufacturing process of the same embodiment.

FIG. 13 is a diagram showing a configuration of an eighth embodiment of the present invention.

FIG. 14 is a view showing the operation of the same embodiment.

FIG. 15 is a diagram showing a driving method according to the embodiment.

16 (a), (b) and (c) are views showing a manufacturing process of the same embodiment.

FIG. 17 is a diagram showing a configuration of a ninth embodiment of the present invention.

FIG. 18 is a perspective view of FIG.

FIG. 19 is a configuration diagram of an actuator, showing a conventional example.

FIG. 20 is an operation explanatory view of the actuator shown in FIG. 19.

FIG. 21 is a diagram showing another conventional example.

FIG. 22 is a view showing still another conventional example.

23 is a displacement characteristic diagram of the conventional example shown in FIG.

[Explanation of symbols]

 1,1 'Bending displacement element K Displacement absorbing part (extension part)

Claims (1)

[Claims] 1. A bending displacement element, which is formed to have a constant length and is displaced in a direction perpendicular to a longitudinal direction based on a driving force applied thereto, wherein the element is formed by applying the driving force. A bending displacement actuator having a displacement absorbing portion that absorbs the generated displacement in the longitudinal direction.