JP2007326204A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator showing excellent rotating characteristics. <P>SOLUTION: The actuator 1 comprises a supporting portion 23; first mass portions 21, 22; a second mass portion 24; first elastic portions 25, 26; second elastic portions 27, 28; and a driving means. The first elastic portions 25, 26 respectively comprise center shaft members 251, 261 extending on a rotation center shaft 100 of the first mass portions 21, 22; and at least a pair of coupling members 252, 253, 262, 263 opposite to each other through the center shaft members 251, 261. By the actuation of the driving means, the pair of the coupling members 252, 253, 262, 263 is bent and deformed in an opposite direction each other. The center shaft members 251, 261 are twisted and deformed to rotate the first mass portions 21, 22. An accompanied with that, the second elastic portions 27, 28 are twisted and deformed to rotate the second mass portion 24. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an actuator.

For example, as an optical scanner for performing drawing by optical scanning with a laser printer or the like, an optical scanner using an actuator composed of a torsional vibrator is known (for example, see Patent Document 1).
Patent Document 1 discloses an actuator including a torsional vibrator having a one-degree-of-freedom vibration system. Such an actuator has a structure in which a mass portion is supported by a torsion spring on both sides thereof as a torsional vibrator of a one-degree-of-freedom vibration system. A light reflecting portion having light reflectivity is provided on the mass portion, and the mass portion is rotationally driven while torsionally deforming the torsion spring, and the light reflecting portion reflects and scans the light. Thereby, drawing can be performed by optical scanning.

  In particular, in the actuator according to Patent Document 1, the torsion spring that connects the mass portion and the support portion has a structure that branches in the middle thereof. That is, the torsion spring according to Patent Document 1 has a first spring portion whose one end is connected to the mass portion, and a second spring portion that branches and extends from the first spring portion and one end is connected to the support portion. ing. That is, the second spring part has a pair of rod-shaped members.

  In such an actuator, the first spring portion is twisted and deformed by bending and deforming each of the pair of rod-shaped members (second spring portions) in opposite directions by the drive source. The mass portion is configured to rotate. By setting it as such a structure, the load required in order to rotate a mass part can be spread | diffused to a 1st spring part and a 2nd spring part, and it becomes a connection part of a 1st spring part. Such stress concentration can be relaxed. Therefore, according to the actuator of Patent Document 1, the mass unit can be largely rotated with a relatively small load.

  However, in the actuator according to Patent Document 1, as described above, since the mass portion is rotated by bending and deforming each of the pair of rod-shaped members in opposite directions, for example, the pair of rod-shaped members are reversed to each other. Depending on the timing of bending deformation in the direction, the rotation center axis of the mass portion at the time of rotation is shaken, and the mass portion cannot be stably rotated. As a result, there arises a problem that the actuator 1 cannot exhibit desired vibration characteristics.

JP 2004-191953 A

  An object of the present invention is to provide an actuator that exhibits excellent rotation characteristics.

Such an object is achieved by the present invention described below.
The actuator of the present invention includes a support portion,
A mass part rotatable with respect to the support part;
An elastic part that supports the mass part so as to be rotatable;
Drive means for rotationally driving the mass part,
An actuator configured to rotate the mass portion while twisting and deforming the elastic portion by operating the driving means;
The elastic part is
A central shaft member extending on the rotational central axis of the mass portion, and at least one pair of connecting members facing each other via the central shaft member;
The mass portion is rotated by twisting and deforming the central shaft member while bending and deforming the pair of connecting members in opposite directions by the operation of the driving means. To do.

  Accordingly, the actuator rotates the mass unit with respect to the support unit while keeping the rotation center axis of the mass unit constant, that is, while suppressing the shake of the rotation center axis of the mass unit. It can be driven. As a result, the mass portion can also be rotated with high accuracy, and the actuator can exhibit desired vibration (rotation) characteristics.

In the actuator of the present invention, the mass part is
A pair of first mass parts;
A second mass part provided between the pair of first mass parts,
The elastic part is
A pair of first elastic parts connecting the support part and the first mass part so that the first mass part is rotatable with respect to the support part;
A pair of second elastic portions connecting the first mass portion and the second mass portion so that the second mass portion is rotatable with respect to the first mass portion; Have
It is preferable that the central shaft member and the pair of connecting members are respectively provided in the first elastic portion.

  As a result, the actuator maintains the rotation center axis of the first mass unit constant, that is, while suppressing the shake of the rotation center axis of the first mass unit, the first mass unit. Can be rotationally driven with respect to the support portion. As a result, the second mass portion can also be rotated with high accuracy, and the actuator can exhibit desired vibration (rotation) characteristics.

In the actuator of the present invention, the mass part is
A first mass part having a frame shape;
A second mass part provided inside the first mass part,
The elastic part is
A pair of first elastic parts connecting the support part and the first mass part so that the first mass part is rotatable with respect to the support part;
A pair of second elastic portions connecting the first mass portion and the second mass portion so that the second mass portion is rotatable with respect to the first mass portion; Have
It is preferable that the central shaft member and the pair of connecting members are respectively provided in the first elastic portion.

  As a result, the actuator maintains the rotation center axis of the first mass unit constant, that is, while suppressing the shake of the rotation center axis of the first mass unit, the first mass unit. Can be rotationally driven with respect to the support portion. As a result, the second mass portion can also be rotated with high accuracy, and the actuator can exhibit desired vibration (rotation) characteristics.

In the actuator of the present invention, the first mass portion has a plate shape,
For the central axis member, the thickness at the width in the direction perpendicular to the rotational axis in the first mass on the surface as W _1, the direction perpendicular to the plane of the first mass When H ₁ , W ₁ is preferably smaller than H ₁ .
Thereby, the rigidity (hardness to strain) of the central shaft member in a direction perpendicular to the surface of the first mass part can be increased. Further, by making W ₁ smaller than H ₁ , the center shaft member can be easily twisted and deformed on the rotation center axis of the first mass portion.

In the actuator of the present invention, the first mass portion has a plate shape,
For each of the pair of connecting members, the width of the first mass portion in the direction perpendicular to the rotation center axis of the first mass portion is W ₂ on the surface of the first mass portion, and the surface of the first mass portion when the thickness at the perpendicular direction is with H ₂ to, W ₂ is preferably larger than H _2.
Thereby, the rigidity (resistance to distortion) of the pair of connecting members in the direction perpendicular to the rotation center axis of the first mass unit on the surface of the first mass unit can be increased.

In the actuator of the present invention, the first mass portion has a plate shape,
The width of the central shaft member in the direction perpendicular to the rotation central axis of the first mass unit is W ₁ on the surface of the first mass unit, and the width is perpendicular to the surface of the first mass unit. the thickness in the direction as H _1,
For each of the pair of connecting members, the width of the first mass portion in the direction perpendicular to the rotation center axis of the first mass portion is W ₂ on the surface of the first mass portion, and the surface of the first mass portion W ₁ and W ₂ satisfy the relationship of W ₁ <W ₂ , and H ₁ and H ₂ satisfy H ₁ > H ₂ where the thickness in the direction perpendicular to H ₂ is H ₂ . It is preferable.
As a result, it is possible to prevent the rotation center axis of the first mass unit from moving in a direction perpendicular to the surface of the first mass unit when the first mass unit is rotationally driven. Furthermore, the rotation center axis of the first mass unit can be prevented from shaking in the direction perpendicular to the rotation center axis of the first mass unit on the surface of the first mass unit. .

In the actuator according to the aspect of the invention, it is preferable that, in each of the first elastic portions, the pair of connecting members is provided substantially symmetrically with respect to the central shaft member.
Accordingly, it is easy to bend and deform the pair of connecting members symmetrically with respect to the rotation center axis of the first mass unit, and as a result, the rotation center axis of the first mass unit is constant. The first mass part can be rotationally driven while maintaining the above.

In the actuator according to the aspect of the invention, it is preferable that each of the pair of connecting members is connected to a distal end portion from a rotation axis of the first mass portion.
Thereby, the space | interval of a pair of said connection member can be enlarged, and the response of the bending deformation of this pair of connection member can be improved.

In the actuator of the present invention, the driving means includes a piezoelectric element that mainly bends and deforms each of the connecting members,
The piezoelectric element is preferably joined to each of the connecting members and configured to bend and deform the pair of connecting members mainly in opposite directions.
Thereby, the first mass unit can be rotated with a relatively simple configuration. In addition, according to this rotational driving method, it is not necessary to arrange a drive source on the rotational trajectory of the first mass unit, so that the rotation angle (runout angle) of the first mass unit is increased. However, the actuator can be miniaturized.

In the actuator of the present invention, it has behavior detection means for detecting the behavior of the second mass part,
The behavior detecting means includes a piezoresistive element provided on the second elastic part, and is configured to detect the behavior of the second mass part based on a change in the resistance value of the piezoresistive element. It is preferable that
Thereby, it is possible to detect the behavior of the second mass unit with high accuracy with a relatively simple configuration.
In the actuator of the present invention, it is preferable that the second mass portion is provided with a light reflecting portion having light reflectivity.
Thereby, the actuator which exhibits the outstanding scanning property can be provided.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of an actuator of the invention will be described with reference to the accompanying drawings.
<First Embodiment>
First, a first embodiment of the actuator of the present invention will be described.
1 is a perspective view showing a first embodiment of the actuator of the present invention, FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, FIG. 3 is a cross-sectional view taken along line BB in FIG. Fig. 5 is a diagram showing an example of the applied AC voltage, Fig. 5 is a graph showing the frequency of the applied AC voltage, and the resonance curves of the first mass portion and the second mass portion, and Fig. 6 is a diagram of the piezoresistive element. It is an enlarged view.

In the following, for convenience of explanation, the upper side in FIGS. 1 to 3 is referred to as “upper”, the lower side is referred to as “lower”, the right side is referred to as “right”, and the left side is referred to as “left”.
As shown in FIG. 1, the actuator 1 includes a base body 2 having a two-degree-of-freedom vibration system, piezoelectric elements 31, 32, 33, 34 for driving the two-degree-of-freedom vibration system of the base body 2, and the base body 2. And a support substrate 4 supported via the bonding layer 5. The base body 2, the support substrate 4, and the bonding layer 5 may be integrally formed.
Moreover, the actuator 1 has a behavior detection means for detecting the behavior of the second mass unit 24 described later.

  The base 2 includes a pair of first mass units (drive units) 21 and 22, a support unit 23, a second mass unit (movable unit) 24, and a pair of first elastic units 25 and 26. And a pair of second elastic portions 27 and 28. In such a base body 2, the second mass portion 24 is centered on the second mass portion 24, and the second elastic portion 27, the first mass portion 21, and the first are arranged on the left side so as to have a symmetrical shape. The elastic portions 25 are sequentially disposed, and the second elastic portion 28, the first mass portion 22, and the first elastic portion 26 are sequentially disposed on the right side.

The pair of first mass portions 21 and 22 each have a plate shape, and have substantially the same dimensions and the same shape.
In addition, a second mass unit 24 is provided between the pair of mass units 21 and 22, and the pair of mass units 21 and 22 is substantially bilaterally symmetric about the second mass unit 24. It is provided to become.

The second mass unit 24 has a plate shape, and a light reflecting unit 241 is provided on the plate surface. Thereby, the actuator 1 can be applied to optical devices such as an optical scanner, an optical attenuator, and an optical switch.
In such first mass parts 21, 22 and second mass part 24, the first mass parts 21, 22 are connected to the support part 23 via the first elastic parts 25, 26, respectively. The second mass portion 24 is connected to the first mass portions 21 and 22 via the second elastic portions 27 and 28.

The first elastic portion 25 connects the first mass portion 21 and the support portion 23 so that the first mass portion 21 can be rotated with respect to the support portion 23. Similarly, the first elastic portion 26 connects the first mass portion 22 and the support portion 23 so that the first mass portion 22 can be rotated with respect to the support portion 23. .
In particular, the first elastic portion 25 includes a central shaft member 251 extending on the rotational central axis 100 of the first mass portion 21 and a central shaft member 251 (that is, the rotational center of the first mass portion 21). And two connecting members 252 and 253 that are opposed to each other via a shaft. Similarly, the first elastic portion 26 includes a central shaft member 261 extending on the rotation central shaft 100 of the first mass portion 22 and two connecting members facing each other via the central shaft member 261. 262, 263.

In the present embodiment, the central shaft members 251 and 261 are rods having substantially the same dimensions and substantially the same shape, and their physical properties (spring constant, etc.) are also substantially the same. The connecting members 252, 253, 262, and 263 have substantially the same dimensions and have substantially the same rod shape, and their physical properties (spring constant and the like) are also substantially the same.
The second elastic portion 27 is a rod-shaped member, and the second mass portion 24 and the first mass portion are configured so that the second mass portion 24 can be rotated with respect to the first mass portion 21. 21 is connected. Similarly, the second elastic portion 28 is a rod-shaped member, and the second mass portion 24 and the second mass portion 24 are configured so that the second mass portion 24 can be rotated with respect to the first mass portion 22. The first mass part 22 is connected.

The first elastic portions 25 and 26 and the second elastic portions 27 and 28 are provided coaxially, and the first mass portions 21 and 22 are arranged with the rotation central axis (rotation axis) as a rotation center axis. The second mass unit 24 is rotatable with respect to the support unit 23 and the first mass units 21 and 22.
As described above, the base body 2 includes the first vibration system composed of the first mass portions 21 and 22 and the first elastic portions 25 and 26, the second mass portion 24 and the second elastic portion 27. , 28 and a second vibration system. That is, the base body 2 has a two-degree-of-freedom vibration system including a first vibration system and a second vibration system. That is, a pair of second elastic portions 27 and 28 are provided on both sides of the second mass portion 24 via the second mass portion 24, and correspondingly, the pair of first mass portions 21 and 22 and the pair of first mass portions 21 and 22 First elastic portions 25 and 26 are provided. Thereby, the 1st mass parts 21 and 22 and the 2nd mass part 24 can be driven more smoothly.

The base body 2 having such a two-degree-of-freedom vibration system is made of, for example, silicon as a main material, and includes first mass parts 21, 22, a second mass part 24, a support part 23, One elastic part 25, 26 and second elastic part 27, 28 are integrally formed.
In order to drive such a two-degree-of-freedom vibration system, piezoelectric elements 31, 32, 33, and 34 are provided on the connecting members 252, 253, 262, and 263 of the first elastic portions 25 and 26, respectively. Is provided.

  The piezoelectric element 31 is joined to the upper surface of the connecting member 252 and configured to expand and contract in the longitudinal direction of the connecting member 252. Thereby, the piezoelectric element 31 bends and deforms the connecting member 252 in the vertical direction by expansion and contraction thereof. The piezoelectric element 32 is bonded to the upper surface of the connecting member 253 and is configured to expand and contract in the longitudinal direction of the connecting member 253. Thereby, the piezoelectric element 32 bends and deforms the connecting member 253 in the vertical direction by expansion and contraction thereof.

  In other words, the piezoelectric element 31 extends along the longitudinal direction of the connecting member 252 and expands and contracts in the extending direction to bend and deform the connecting member 252. Accordingly, the connecting member 252 can be bent and deformed by the piezoelectric element 31 with a relatively simple configuration. Similarly, the piezoelectric element 32 extends along the longitudinal direction of the connecting member 253 and expands and contracts in the extending direction to bend and deform the connecting member 253. Accordingly, the connecting member 253 can be bent and deformed by the piezoelectric element 32 more reliably with a relatively simple configuration.

  More specifically, the piezoelectric element 31 includes a piezoelectric layer 311 composed of a piezoelectric material as a main material, and a pair of electrodes 312 and 313 that sandwich the piezoelectric layer 311. The electrode 312 located on the lower side in FIG. 2 is bonded to the upper surface of the connecting member 252. When the piezoelectric element 31 is configured as described above, the connecting member 252 can be bent and deformed by the piezoelectric element 31 with a relatively simple configuration.

The piezoelectric layer 311 covers the entire upper surface of the connecting member 252 and is provided so as to straddle the joint portion between the connecting member 252 and the support portion 23. Thereby, the driving force of the piezoelectric element 31 can be efficiently transmitted by the connecting member 252. As a result, the driving voltage can be further reduced and the connecting member 252 can be bent and deformed more greatly.
Examples of the piezoelectric material include zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate, lead zirconate titanate (PZT), barium titanate, and various other materials. One or more of them can be used in combination, but at least one of zinc oxide, aluminum nitride, lithium tantalate, lithium niobate, potassium niobate and lead zirconate titanate is mainly used. Are preferred. By configuring the piezoelectric layer 311 with such a material, the actuator 1 can be driven at a higher frequency.

The electrode 312 is longer than the piezoelectric layer 311, and can be connected to a power source (not shown) on the support portion 23. on the other hand. The electrode 313 has substantially the same length as that of the piezoelectric layer 311. And the electrode 313 is connected to the terminal 314 provided on the support part 23 via the wiring formed, for example by wire bonding, and connection with a power supply (not shown) is possible.
In such a piezoelectric element 31, when a voltage is applied between the electrode 312 and the electrode 313 (terminal 314), the piezoelectric layer 311 expands and contracts in parallel with the longitudinal direction of the connecting member 252 due to the electrostrictive effect. Thereby, the piezoelectric element 31 bends and deforms the connecting member 252 in the vertical direction by expansion and contraction thereof.

Like the piezoelectric element 31, the piezoelectric element 32 is configured, and when a voltage is applied between the electrode 322 and the terminal 324, a piezoelectric layer (not shown) in the piezoelectric element 32 is changed to its electric current. Due to the distortion effect, the connecting member 253 expands and contracts parallel to the longitudinal direction. Thereby, the piezoelectric element 32 bends and deforms the connecting member 253 in the vertical direction by expansion and contraction thereof.
Since such piezoelectric elements 31 and 32 are both provided on the upper surface of the base 2, the two connecting members 252 and 253 are mainly bent and deformed in opposite directions when operated to alternately expand and contract. Let As a result, the entire first elastic portion 25 having the two connecting members 252 and 253 is torsionally deformed.

  Similarly to the piezoelectric elements 31 and 32 described above, the piezoelectric elements 33 and 34 are configured. That is, regarding the piezoelectric element 33, when a voltage is applied between the electrode 332 and the electrode 333 (terminal 334), the piezoelectric layer 331 in the piezoelectric element 33 is parallel to the longitudinal direction of the connecting member 262 due to its electrostrictive effect. Extends and contracts. Thereby, the piezoelectric element 33 bends and deforms the connecting member 262 in the vertical direction by the expansion and contraction. Further, regarding the piezoelectric element 34, when a voltage is applied between the electrode 342 and the terminal 344, a piezoelectric layer (not shown) in the piezoelectric element 34 is parallel to the longitudinal direction of the connecting member 263 due to its electrostrictive effect. Extends and contracts. Thereby, the piezoelectric element 34 bends and deforms the connecting member 263 in the vertical direction by expansion and contraction thereof.

  Since the piezoelectric elements 33 and 34 are provided on the upper surface of the base 2 in the same manner as the piezoelectric elements 31 and 32, the pair of connecting members 262 and 263 are moved in opposite directions when operated alternately. Mainly bending deformation. As a result, the entire first elastic portion 26 having the pair of connecting members 262 and 263 is torsionally deformed. Thereby, the 1st mass part 22 can be rotated with a comparatively simple structure. Further, according to this rotation driving method, it is not necessary to arrange a drive source on the rotation path of the first mass unit 22, so that the rotation angle (swing angle) of the first mass unit is increased. Meanwhile, the actuator 1 can be downsized.

The support substrate 4 for supporting the base 2 as described above is bonded to the base 2 via the bonding layer 5. The bonding layer 5 is made of, for example, glass, silicon, or SiO ₂ as a main material.
Further, the support substrate 4 is made of, for example, glass or silicon as a main material.
As shown in FIGS. 2 and 3, an opening 41 is formed on the upper surface of the support substrate 4 at a portion corresponding to the second mass portion 24.
The opening 41 constitutes an escape portion that prevents contact with the support substrate 4 when the second mass portion 24 rotates (vibrates). By providing the opening (escape portion) 41, the deflection angle (amplitude) of the second mass portion 24 can be set larger while preventing the actuator 1 from being enlarged.

Note that the relief portion as described above is not necessarily opened (opened) on the lower surface (the surface opposite to the second mass portion 24) of the support substrate 4 as long as the above-described effect can be sufficiently exerted. May be. In other words, the escape portion can be configured by a recess formed on the upper surface of the support substrate 4.
Each piezoelectric element 31, 32, 33, 34 is connected to a power source (not shown), and is configured such that an alternating voltage (drive voltage) can be applied between the electrodes of each piezoelectric element 31, 32, 33, 34.

The actuator 1 having the above configuration is driven as follows.
For example, a voltage as shown in FIG. 4A is applied to the piezoelectric elements 32 and 34, and a voltage as shown in FIG. 4B is applied to the piezoelectric elements 31 and 33. In other words, voltages that are 180 ° out of phase with each other are applied to the piezoelectric elements 32 and 34 and the piezoelectric elements 31 and 33. Then, the piezoelectric elements 31 and 33 are in an expanded state, the piezoelectric elements 32 and 34 are in a contracted state, and the piezoelectric elements 31 and 33 are in a contracted state and the piezoelectric elements 32 and 34 are in an expanded state. And are repeated alternately.
Accordingly, the first elastic portions 25 and 26 are twisted and deformed, and the first mass portions 21 and 22 rotate (vibrate) with respect to the support portion 23.

  At this time, each of the connecting members 252, 253, 262, and 263 mainly bends and deforms, so that the entire first elastic portion 25 and the entire first elastic portion 26 are torsionally deformed. Can be reduced. Therefore, it can be driven with a large deflection angle. At this time, the central shaft members 251 and 261 are torsionally deformed on the rotation central shaft 100.

Further, since the driving force is obtained by the piezoelectric elements 31, 32, 33, and 34, it is possible to drive with a relatively large driving force even when driving at a low voltage. Therefore, even in low voltage driving, the spring constants of the first elastic portions 25 and 26 can be increased and driving can be performed at high frequency. In particular, since the driving force of the piezoelectric elements 31, 32, 33, and 34 is relatively high, the deflection angle can be increased even if the spring constants of the first elastic portions 25 and 26 are relatively high.
The second mass part 24 connected via the second elastic parts 27, 28 with the vibration (drive) of the first mass parts 21, 22 is also connected to the second elastic part 27, 28 is oscillated (rotated) so as to be inclined with respect to the plate surface of the support substrate 4 (the paper surface in FIG. 1).

Next, the first elastic part will be described in detail. Since the first elastic portions 25 and 26 have the same configuration (including dimensions, shape, physical characteristics, etc.), the first elastic portion 25 will be described as a representative, and the first elastic portion The description of 26 is omitted.
For convenience of explanation, on the surface of the base 2, the direction perpendicular to the rotation central axis 100 is defined as the X direction, the direction parallel to the rotation central axis 100 is defined as the Y direction, and the direction perpendicular to the surface of the base 2. Is the Z direction. Also, the width of the central shaft member 251 in the X direction is _{W 1,} the width of the connecting member 252 and 253 in the X-direction and _{W 2,} and the thickness of the central shaft member 251 in the Z-direction and _{H 1,} Z the thickness of the connecting member 252 and 253 in the direction to _{H 2.}

  As described above, the first elastic portion 25 includes two central shaft members 251 extending on the rotation center shaft 100 and two opposite to each other via the center shaft member 251 (that is, the rotation center shaft 100). The connecting members 252 and 253 are configured. Thus, by providing the central shaft member 251 on the rotation center shaft 100, the actuator 1 keeps the rotation center shaft 100 constant, that is, the shake of the rotation center shaft 100 (particularly in the Z-axis direction). The first mass portion 21 can be rotationally driven with respect to the support portion 23 while suppressing blurring. As a result, the second mass portion 24 can also be rotated with high accuracy, and the actuator 1 can exhibit desired vibration (rotation) characteristics.

The central shaft member 251 preferably has W ₁ smaller than H ₁ . That is, it is preferable that the central shaft member 251 has a substantially rectangular cross-sectional shape with the Z-axis direction as a longitudinal direction. By adopting such a cross-sectional shape, the rigidity (resistance to distortion) of the central shaft member 251 in the Z-axis direction can be increased. Further, by making W ₁ smaller than H ₁ , it can be easily twisted and deformed on the rotation center axis 100. That is, the central shaft member 251 is configured to prevent the rotation of the first mass unit 21 due to the bending deformation of the connecting members 252 and 253 while suppressing the rotation of the first mass unit 21 during the rotation drive. The shake of the shaft 100 in the Z-axis direction can be effectively prevented. Thereby, the 1st mass part 21 can be rotationally driven, keeping the rotation center axis | shaft 100 constant. As a result, the actuator 1 can exhibit a desired vibration (rotation) characteristic and can be driven at a low voltage.

The connecting member 252 and 253 is preferably _{W 2} is greater than _{H 2.} That is, it is preferable that the connecting members 252 and 253 have a substantially rectangular cross-sectional shape with the X-axis direction as a longitudinal direction. By setting it as such a cross-sectional shape, the rigidity (hardness to distortion) of the connection member 252 to the X-axis direction can be improved. Further, the connecting members 252 and 253 can be easily bent and deformed in the Z direction by the piezoelectric element 31. That is, the connecting members 252 and 253 effectively prevent the rotation center shaft 100 from shaking in the X-axis direction when the first mass portion 21 is driven to rotate, and the Z-axis by the piezoelectric elements 31 and 32. The bending deformation in the direction can be easily performed. Thereby, the 1st mass part 21 can be rotationally driven, keeping the rotation center axis | shaft 100 constant. As a result, the actuator 1 can exhibit a desired vibration (rotation) characteristic and can be driven at a low voltage.

In the present embodiment, the connecting member 252 and the connecting member 253 have the same shape and the same dimensions, and the same physical properties (such as rigidity).
Further, as described above, it is more preferable that W ₁ is larger than H ₁ and W ₂ is smaller than H ₂ as in the present embodiment. That is, the cross-sectional shape of the central shaft member 251 has a substantially rectangular shape with the Z-axis direction as the longitudinal direction, and the cross-sectional shape of the connecting members 252 and 253 has a substantially rectangular shape with the X-axis direction as the longitudinal direction. preferable. With such a configuration, the center shaft member 251 prevents the rotation center shaft 100 from shaking in the Z-axis direction when the first mass portion 21 is driven to rotate, and the connection members 252 and 253 It is possible to prevent the rotation center shaft 100 from shaking in the X-axis direction. Thereby, the 1st mass part 21 can be rotationally driven, keeping the rotation center axis | shaft 100 constant. As a result, the second mass unit 24 can be driven to rotate more stably (highly accurately), and the actuator 1 can exhibit desired vibration (rotation) characteristics.

Further, in the first elastic portion 25, it is preferable that W ₁ and W ₂ satisfy the relationship of W ₁ <W ₂ , and H ₁ and H ₂ satisfy H ₁ > H ₂ . With such a configuration, the center shaft member 251 prevents the rotation center shaft 100 from shaking in the Z-axis direction when the first mass portion 21 is driven to rotate, and the connection members 252 and 253 It is possible to prevent the rotation center shaft 100 from shaking in the X-axis direction. Further, the central shaft member 251 is prevented from obstructing the rotational drive of the first mass portion 21, and the bending deformation of the connecting members 252 and 253 in the Z-axis direction is facilitated. As a result, the actuator 1 can exhibit a desired vibration (rotation) characteristic and can be driven at a low voltage.

  The connecting member 252 and the connecting member 253 are provided for the center axis member 251 (that is, the rotation center axis 100) in plan view. Accordingly, it becomes easy to bend and deform the connecting member 252 and the connecting member 253 symmetrically with respect to the rotation center axis 100. As a result, the first mass portion 21 can be rotated while keeping the rotation center axis 100 constant. It can be driven dynamically.

  In the actuator 1 of the present embodiment, the connecting member 252 and the connecting member 253 are provided in parallel to each other. However, if the first mass portion 21 can be rotatably supported with respect to the support portion 23, For example, the interval between the connecting member 252 and the connecting member 253 gradually decreases from the boundary portion between the connecting member 252 and the support portion 23 toward the boundary portion between the connecting member 252 and the first mass portion 21. Or you may provide so that it may increase gradually. That is, the connecting member 252 and the connecting member 253 may be provided in a substantially “C” shape.

  Each of the pair of connecting members 252 and 253 is connected to the distal end of the first mass portion 21 from the rotation center axis 100. Thereby, the space | interval of the connection member 252 and the connection member 253 can be enlarged, and the response of the bending deformation of the connection members 252 and 253 by the piezoelectric elements 31 and 32 can be improved. As a result, for example, it is possible to suppress a deviation from occurring in the timing at which the connecting members 252 and 253 are bent and deformed. Therefore, the first mass portion 21 can be rotationally driven while keeping the rotational central axis 100 constant, and the actuator 1 can exhibit desired vibration (rotation) characteristics.

Next, the relationship between the first mass parts 21 and 22 and the second mass part 24 will be described in detail.
The first mass portion 21, the length in the X-axis direction (longitudinal direction) (the maximum length) and _{L 1} from the rotational axis 100, the first mass portion 22, the X-axis from the rotational axis 100 When the length (maximum length) in the direction (longitudinal direction) is L ₂ and the length (maximum length) in the X-axis direction from the rotation central axis 100 is L ₃ for the second mass portion 24, In the present embodiment, since the first mass parts 21 and 22 are provided independently, the first mass part 21 regardless of the size (length L ₃ ) of the second mass part 24. 22 and the second mass part 24 do not interfere with each other, and L ₁ and L ₂ can be reduced. Thereby, the rotation angle (swing angle) of the first mass parts 21 and 22 can be increased, and as a result, the rotation angle of the second mass part 24 can be increased.

Here, the dimension of the first mass portions 21 and 22 and the second mass 24, _{respectively,} preferably set to satisfy L 1 _{<L 3} and _L 2 _{<L 3} becomes relevant.
By satisfying the above relationship, L ₁ and L ₂ can be made smaller, the rotation angle of the first mass parts 21 and 22 can be made larger, and the rotation angle of the second mass part 24 can be further increased. Can be bigger.

In this case, it is preferable that the maximum rotation angle of the second mass unit 24 is configured to be 20 ° or more.
By these, the low voltage drive of the 1st mass parts 21 and 22 and the vibration (rotation) in the large rotation angle of the 2nd mass part 24 are realizable.
For this reason, when such an actuator 1 is applied to, for example, an optical scanner used in an apparatus such as a laser printer or a scanning confocal laser microscope, the apparatus can be more easily downsized.

As described above, in the present embodiment, L ₁ and L ₂ are set to be substantially equal, but it goes without saying that L ₁ and L ₂ may be different.
By the way, in such a vibration system (two-degree-of-freedom vibration system) including the mass parts 21, 22, and 24, the amplitude (deflection angle) of the first mass parts 21 and 22 and the second mass part 24, and the piezoelectric element A frequency characteristic as shown in FIG. 5 exists between the frequency of the alternating voltage applied to 31, 32, 33, and 34.

That is, the vibration system includes two resonance frequencies fm ₁ [kHz] and fm ₃ [kHz] (however, fm) in which the amplitude of the first mass parts 21 and 22 and the amplitude of the second mass part 24 are increased. ₁ <fm ₃ ) and one anti-resonance frequency fm ₂ [kHz] at which the amplitude of the first mass parts 21 and 22 is substantially zero.
In this vibration system, the frequency F of the AC voltage applied to the piezoelectric elements 31, 32, 33, 34, those lower of the two resonant frequencies, i.e., preferably set to be substantially equal to fm _1. Thereby, the deflection angle (rotation angle) of the second mass unit 24 can be increased while suppressing the amplitude of the first mass units 21 and 22.
In this specification, F [kHz] and fm ₁ [kHz] being substantially equal means that the condition of (fm ₁ −1) ≦ F ≦ (fm ₁ +1) is satisfied.

The average thicknesses of the first mass parts 21 and 22 are each preferably 1 to 1500 μm, and more preferably 10 to 300 μm.
The average thickness of the second mass part 24 is preferably 1-1500 μm, and more preferably 10-300 μm.
Such an actuator 1 has behavior detecting means for detecting the behavior of the second mass part (movable part) 24. Thereby, the actuator 1 can perform more stable rotation drive, and can exhibit a desired vibration (rotation) characteristic.

The behavior detection means includes a piezoresistive element (piezoresistive element) 70 provided in the second elastic portion 28, and detects the behavior of the second mass portion 24 based on a change in the resistance value of the piezoresistive element 70. Is configured to do. Thereby, the behavior of the second mass unit 24 can be detected with high accuracy with a relatively simple configuration.
The piezoresistive element 70 is provided at substantially the center of the upper surface of the second elastic portion 28 (on the surface opposite to the support substrate 4). Such a piezoresistive element 70 can be provided by, for example, diffusing (doping) boron, phosphorus or the like to form a diffusion layer.
Such a piezoresistive element 70 has the property that the resistance value changes according to the distortion (deformation amount) by being distorted by an external force (stress). Therefore, when the second elastic portion 28 is torsionally deformed, the resistance value of the piezoresistive element 70 changes according to the distortion (deformation amount).

  As shown in FIG. 6, the piezoresistive element 70 includes a pair of input electrodes 81 and 82 (hereinafter also simply referred to as “electrodes”) and a pair of output electrodes 83 and 84 (hereinafter simply referred to as “electrodes”). Are connected). The electrode 81 and the electrode 82 are juxtaposed along the X-axis direction, and the electrode 83 and the electrode 84 are juxtaposed along the Y-axis direction. The electrodes 81 to 84 are provided so that a straight line connecting the electrode 81 and the electrode 82 and a straight line connecting the electrode 83 and the electrode 84 are orthogonal to each other at substantially the center of each straight line. Furthermore, the electrodes 81 to 84 are arranged so that the intersection point is approximately the center of the piezoresistive element 70. By providing the electrodes 81 to 84 in this manner, a change in the resistance value of the piezoresistive element 70 caused by the torsional deformation of the second elastic portion 28 can be detected with high sensitivity. That is, the shear strain generated in the second elastic portion 28 can be detected with high sensitivity.

Such a piezoresistive element 70 is configured to apply a bias voltage to the electrode 81 and the electrode 82 by a power source (not shown). When the second elastic portion 28 is torsionally deformed in this state (a state where a bias voltage is applied), the resistance value of the piezoresistive element 70 also changes according to the amount of deformation. Accordingly, since the current value or voltage value flowing through the electrodes 83 and 84 also changes in accordance with such a change, by detecting the current value or voltage value at the electrodes 83 and 84, the second mass unit 24 Behavior can be detected.
Thus, based on the behavior of the second mass part 24 detected by the behavior detection means, the rotation drive of the actuator 1 can be controlled by the control means (not shown). Thereby, the actuator 1 can exhibit desired vibration (rotation) characteristics.

  Moreover, each electrode 81-84 provided in the piezoresistive element 70 is connected with the electrodes 811-841 provided in the support part 23 by the wiring 812-842 as shown in FIG. This facilitates connection of a power source or the like (not shown). Moreover, since it can connect with a power supply etc. in the support part 23, it can prevent affecting the rotational drive of the actuator 1. FIG.

  The wiring lead-out paths of the electrodes 81 to 84 are, in order from the respective electrodes 81 to 84, the second elastic portion 28, the first mass portion 22, the central shaft member 261, and the support portion 23. Further, the patterning of the wirings 812 to 814 is performed linearly. From this point of view, it can be said that the central shaft member 261 functions as a path for the wirings 812 to 842 for drawing the electrodes 81 to 84 to the support portion 23. That is, if the central shaft member 261 is not provided, the electrodes 81 to 84 cannot be drawn out to the support portion 23 without passing through the connecting member 262 (or connecting member 263). In this case, The wirings 812 to 842 need to be patterned via the lower surface of the connecting member 262, or the wirings 812 to 842 need to be patterned via an insulating layer between the surface of the connecting member 262 and the piezoelectric element 33. Becomes complicated. However, such a problem can be prevented by providing the central shaft member 261. Furthermore, since the central shaft member 261 and the second elastic portion 28 are provided coaxially, the wires 812- 842 can be linearly patterned, and the wirings 812 to 842 can be more easily patterned.

  In the present embodiment, the behavior of the second mass unit 24 is detected by using one piezoresistive element 70. However, if the behavior of the second mass unit 24 can be detected, For example, a pair of piezoresistive elements are provided on the second elastic parts 27 and 28 symmetrically with respect to the second mass part 24, and current values or voltage values obtained from the respective piezoresistive elements. By amplifying this change by a differential amplifier circuit (not shown), the behavior of the second mass unit 24 can be detected more accurately.

Such an actuator 1 can be manufactured as follows, for example.
FIG. 7 is a view (longitudinal sectional view) for explaining the manufacturing method of the actuator 1 of the first embodiment. FIG. 7 shows a cross section corresponding to the cross section taken along the line AA in FIG. In the following, for convenience of explanation, the upper side in FIG. 7 is referred to as “upper” and the lower side is referred to as “lower”.

[A1]
First, as shown in FIG. 7A, an SOI substrate 6 in which an Si layer 61, an SiO ₂ layer 62, and an Si layer 63 are sequentially stacked is prepared, and one surface of the SOI substrate 6 (surface on the Si layer 61 side) is prepared. ), Electrodes 312, 322, 332, 342 and terminals 314, 324, 334, 344 are formed.
The electrodes 312, 322, 332, 342 and the terminals 314, 324, 334, 344 are formed by forming a metal film on the SOI substrate 6 and forming the electrodes 312, 322, 332, 342 and the terminals 314, 324, 334, 344. After the metal film is etched through a resist mask having a shape corresponding to the shape, the resist mask is removed.

  Examples of the metal film forming method include chemical vapor deposition (CVD) such as plasma CVD, thermal CVD, and laser CVD, dry plating methods such as vacuum deposition, sputtering, and ion plating, electrolytic plating, immersion plating, and nothing. Wet plating methods such as electrolytic plating, thermal spraying, and joining of sheet-like members can be used. Note that the same method can also be used for forming a metal film in the following steps.

  As an etching method, for example, one or more of physical etching methods such as plasma etching, reactive ion etching, beam etching, and light-assisted etching, and chemical etching methods such as wet etching are used in combination. be able to. Note that the same method can be used for etching in the following steps.

[A2]
Next, as shown in FIG. 7B, piezoelectric layers 311, 321, 331, and 341 are formed on the electrodes 312, 322, 332, and 342.
The piezoelectric layers 311, 321, 331, and 341 can be formed by sol-gel method, sputtering, aerosol deposition method, or the like.

[A3]
Next, as shown in FIG. 7C, a part of the Si layer 61 of the SOI substrate 6 is removed, and the first mass parts 21, 22, the support part 23, the second mass part 24, The elastic portions 25 and 26 and the second elastic portions 27 and 28 are formed. Thereby, the base 2 is obtained.
The formation of the first mass parts 21, 22, the support part 23, the second mass part 24, the first elastic parts 25, 26 and the second elastic parts 27, 28 forms a metal film on the SOI substrate 6. A resist having a shape corresponding to the shapes of the first mass portions 21 and 22, the support portion 23, the second mass portion 24, the first elastic portions 25 and 26, and the second elastic portions 27 and 28. After the metal film is etched through the mask, the resist mask is removed.
At this time, the SiO ₂ layer as an intermediate layer of the SOI substrate 6 functions as a stop layer for the etching.
As an etching method, the same method as the above-mentioned step [A1] can be used.

[A4]
Next, as shown in FIG. 7D, a part of the Si layer 63 of the SOI substrate 6 is removed to form a recess (opening 41).
As a method for forming the recess, the same method as in the above-described step [A3] can be used.

[A5]
Next, as shown in FIG. 7E, electrodes 313, 323, 333, 343 corresponding to these are formed on the piezoelectric layers 311, 321, 331, 341, and on the second mass part 24. The light reflecting portion 241 is formed in Further, the bonding layer 5 is formed by removing a part of the SiO ₂ layer 62 of the SOI substrate 6.
As a method for forming the electrodes 313, 323, 333, 343 and the light reflecting portion 241, a method similar to the above-described step [A1] can be used.

[A6]
Next, as shown in FIG. 7F, half-etching is performed from the space 41 side (the lower side in FIG. 7) so that the connecting members 252, 253, 262, and 263 have a predetermined thickness.
Then, boron, phosphorus or the like is diffused (doped) into the second elastic portion 28 to form the piezoresistive element 70, and the electrodes 81 to 84 are connected to the piezoresistive element 70.
On the other hand, the electrodes 811 to 841 are disposed on the support portion 23. And each electrode 81-84 and each electrode 811-841 are connected by wiring 812-842.
As described above, the actuator 1 of the first embodiment is manufactured.

Second Embodiment
Next, a second embodiment of the actuator of the present invention will be described.
FIG. 8 is a perspective view showing a second embodiment of the actuator of the present invention. In the following, for convenience of explanation, the upper side in FIG. 8 is referred to as “upper”, the lower side as “lower”, the right side as “right”, and the left side as “left”.

Hereinafter, the actuator of the second embodiment will be described focusing on the differences from the actuator of the first embodiment described above, and the description of the same matters will be omitted.
The actuator 1A of the second embodiment is substantially the same as the actuator 1 of the first embodiment except that the configuration of the first mass portion 21A is different.
That is, the actuator 1A shown in FIG. 8 has a first mass portion 21A having a frame shape and a second mass portion 24 provided inside the first mass portion 21A. The first elastic portions 25 and 26 are connected to the first mass portion 21 as described above. That is, the central shaft members 251 and 261 and the connecting members 252, 253, 262, and 263 are joined to one first mass portion 21 A. Accordingly, the first mass portion 21A can be rotationally driven by the pair of first elastic portions 25 and 26. Thereby, for example, the desired vibration characteristics can be exhibited by shifting the timing of the rotational drive of the pair of first mass parts 21 and 22 that may occur in the case of the actuator 1 described in the first embodiment. The problem of being unable to do so can be prevented. That is, according to the actuator 1A of the present embodiment, the second elastic portions 27 and 28 are twisted and deformed by the rotation of the first mass portion 21A. It can be done at the timing. As a result, the second mass unit 24 can be rotated with higher accuracy, and the actuator 1 can exhibit desired vibration (rotation) characteristics.

The actuator of the present invention has been described based on the illustrated embodiment, but the present invention is not limited to this. For example, in the actuator of the present invention, the configuration of each part can be replaced with an arbitrary configuration that exhibits the same function, and an arbitrary configuration can be added.
In the above-described embodiment, the connecting member has a linear shape. However, the first elastic connecting portion as a whole can be twisted and deformed by bending the two connecting members mainly in opposite directions. If so, the shape of the connecting member is arbitrary. For example, the connecting member may be curved. Further, the cross-sectional shape of the connecting member may be, for example, an elliptical shape, each corner of the rectangle may be rounded, or may be an irregular shape.

In the above-described embodiment, only one central shaft member is provided for each first elastic portion. However, for example, two central shaft members may be provided in parallel along the Z-axis direction. Good. Further, the shape of the central shaft member is arbitrary as long as the first mass portion can be rotationally driven while keeping the rotational central shaft 100 constant.
In the above-described embodiment, the piezoelectric element is bonded to the upper surface of the connecting member. However, the arrangement of the piezoelectric element is arbitrary as long as the connecting member can be bent and deformed mainly in the opposite directions.

In the above-described embodiment, a structure has been described in which the shape is substantially symmetric (symmetric) with respect to a plane that passes through the center of the actuator and is perpendicular to the rotation axis of the first mass portion and the second mass portion. However, it may be asymmetric.
In the above-described embodiment, the configuration in which the light reflecting portion is provided on the upper surface of the second mass portion (the surface opposite to the support substrate) has been described. For example, the light reflecting portion is provided on the opposite surface. The structure which is provided may be sufficient and the structure provided in both surfaces may be sufficient.
In the above-described embodiment, the two-degree-of-freedom vibration system has been described. However, for example, it may be used for a one-degree-of-freedom vibration system actuator. In this case, for example, the first mass parts 21 and 22, the second elastic parts 27 and 28, and the second mass part 24 can be used as a mass part of a one-degree-of-freedom vibration system.

It is a perspective view which shows 1st Embodiment of the actuator of this invention. It is the sectional view on the AA line in FIG. It is the BB sectional view taken on the line in FIG. It is a figure which shows an example of the alternating voltage to apply. It is a graph which shows the frequency of the applied alternating voltage, and the resonance curve of a 1st mass part and a 2nd mass part. It is an enlarged view of a piezoresistive element. It is a figure explaining the manufacturing method of an actuator. It is a perspective view which shows 2nd Embodiment of the actuator of this invention.

Explanation of symbols

1, 1A ... Actuator 2 ... Base 21, 22, 21A ... First mass part (drive part) 23 ... Support part 24 ... Second mass part 241 ... Light reflection Portions 25, 26, etc. First elastic portion 251, 261 ... Center shaft member 252, 253, 262, 263 ... Connecting member 27, 28 ... Second elastic portion 31, 32, 33, 34 ... Piezoelectric elements 311, 321, 331, 341 ... Piezoelectric layers 312, 313, 322, 323, 332, 333, 342, 343 ... Electrodes 314, 324, 334, 344 ... Terminal 4 Support substrate 41 Opening 5 Junction layer 6 SOI substrate 61 Si layer 62 SiO ₂ layer 63 Si layer 70 Piezoresistive element 81 , 811, 82, 821... Input electrode (electric ) 83,831,84,841 ‥‥‥ output electrode (electrode) 812,822,832,842 ‥‥‥ wiring 100 ‥‥‥ rotational axis

Claims (11)

A support part;
A mass part rotatable with respect to the support part;
An elastic part that supports the mass part to be rotatable;
Drive means for rotationally driving the mass part,
An actuator configured to rotate the mass portion while twisting and deforming the elastic portion by operating the driving means;
The elastic part is
A central shaft member extending on the rotational central axis of the mass portion, and at least one pair of connecting members facing each other via the central shaft member;
The mass mechanism is configured to rotate by twisting and deforming the central shaft member while bending and deforming the pair of connecting members in opposite directions by the operation of the driving means. Actuator to do. The mass part is
A pair of first mass parts;
A second mass part provided between the pair of first mass parts,
The elastic part is
A pair of first elastic parts connecting the support part and the first mass part so that the first mass part is rotatable with respect to the support part;
A pair of second elastic portions connecting the first mass portion and the second mass portion so that the second mass portion is rotatable with respect to the first mass portion; Have
The actuator according to claim 1, wherein the central shaft member and the pair of connecting members are provided in the first elastic portion, respectively. The mass part is
A first mass part having a frame shape;
A second mass part provided inside the first mass part,
The elastic part is
A pair of first elastic parts connecting the support part and the first mass part so that the first mass part is rotatable with respect to the support part;
A pair of second elastic portions connecting the first mass portion and the second mass portion so that the second mass portion is rotatable with respect to the first mass portion; Have
The actuator according to claim 1, wherein the central shaft member and the pair of connecting members are provided in the first elastic portion, respectively. The first mass part has a plate shape,
For the central axis member, the thickness at the width in the direction perpendicular to the rotational axis in the first mass on the surface as W _1, the direction perpendicular to the plane of the first mass when the H _{1, W 1,} the actuator according to _{H 1} smaller claim 2 or 3. The first mass part has a plate shape,
For each of the pair of connecting members, the width of the first mass portion in the direction perpendicular to the rotation center axis of the first mass portion is W ₂ on the surface of the first mass portion, and the surface of the first mass portion when the thickness at the perpendicular direction is with H ₂ to, W ₂ is actuator according in H ₂ greater claim 4. The first mass part has a plate shape,
The width of the central shaft member in the direction perpendicular to the rotation central axis of the first mass unit is W ₁ on the surface of the first mass unit, and the width is perpendicular to the surface of the first mass unit. the thickness in the direction as H _1,
For each of the pair of connecting members, the width of the first mass portion in the direction perpendicular to the rotation center axis of the first mass portion is W ₂ on the surface of the first mass portion, and the surface of the first mass portion W ₁ and W ₂ satisfy the relationship of W ₁ <W ₂ , and H ₁ and H ₂ satisfy H ₁ > H ₂ where the thickness in the direction perpendicular to H ₂ is H ₂ . The actuator according to claim 4 or 5.   The actuator according to any one of claims 2 to 6, wherein in each of the first elastic portions, the pair of connecting members are provided substantially symmetrically with respect to the central shaft member.   The actuator according to any one of claims 2 to 7, wherein each of the pair of connecting members is connected to an end portion on a distal side from a rotation axis of the first mass portion. The driving means includes a piezoelectric element that mainly bends and deforms each of the connecting members,
The actuator according to any one of claims 2 to 8, wherein the piezoelectric element is joined to each of the connecting members, and is configured to bend and deform the pair of connecting members mainly in directions opposite to each other. Having a behavior detecting means for detecting the behavior of the second mass part;
The behavior detecting means includes a piezoresistive element provided on the second elastic part, and is configured to detect the behavior of the second mass part based on a change in the resistance value of the piezoresistive element. The actuator according to any one of claims 2 to 9, wherein The actuator according to any one of claims 2 to 10, wherein the second mass portion is provided with a light reflecting portion having light reflectivity.

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