JP3814100B2 - Piezoelectric actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of a piezoelectric actuator in which a moving body can be easily reciprocated and can easily realize a configuration and functions in a minute size.
[0002]
[Prior art]
FIG. 7 is a perspective view showing an example of a conventional piezoelectric actuator. This piezoelectric actuator 300 is used as an XY stage for movement at a minute distance, and is configured to move in each axial direction by a laminated piezoelectric element. A metal plate is punched into the fixed base 301 by wire discharge or a mold process, and a movable table 303 is disposed in the punched portion 302. Support springs 304 are formed on the four sides of the movable table 303, and guide portions 305 are attached to the four sides of the movable table 303 via the support springs 304. A laminated piezoelectric element 306 is attached to the end of the guide portion 305 in a direction perpendicular to the movable table 303.
[0003]
FIG. 8 shows an enlarged plan view of the support spring 304. The support spring 304 has a rectangular frame shape, with the long side 304a being narrow and the short side 304b being wide. This is because the movable table 303 via the support spring 304 has a longer side 304a having a narrower width and a longer side 304 having a longer length, so that the stress relative to the displacement is exponentially or proportionally due to mechanical characteristics. Therefore, the long side 304a has a structure with a degree of freedom for movement in the X-axis direction in the drawing in the width direction. Similarly, as shown in FIG. 9, the aspect ratio (b / a) of the thickness b to the width a is set to 1 or more, and the torsional displacement when the movable table 303 is moved is suppressed.
[0004]
When the piezoelectric actuator 300 moves in the X direction, the piezoelectric actuator 300 is displaced by applying a predetermined voltage to the stacked piezoelectric element 306 for moving in the X direction. When the laminated piezoelectric element 306 is displaced in the thickness direction, the movable table 303 connected by the guide portion 305 is also displaced in the X direction. At this time, the support spring 304 formed on the side in the X direction is deformed in the short side direction. The X-direction guide unit 305 has a function as an X-direction guide for the movable table 303. On the other hand, the support springs 304 formed on the sides in the Y direction are not easily deformed in the long side direction, so that it is difficult to absorb the displacement of the multilayer piezoelectric element 306. The same effect is obtained when moving in the Y direction.
[0005]
[Problems to be solved by the invention]
However, since the conventional piezoelectric actuator 300 generally uses the multilayer piezoelectric element 306, it is necessary to first create the multilayer piezoelectric element 306 according to this specification. The multilayer piezoelectric element 306 is generally manufactured by a green sheet method. When this manufacturing process is used, a green sheet is prepared from a slurry, and a conductive paste for internal electrodes is screen-printed on the green sheet. A green sheet is laminated and fired. As a feature of the multilayer piezoelectric element obtained from this configuration, a strong generated force can be obtained, but a minute displacement amount can be obtained. Further, the laminated piezoelectric element 306 thus prepared is incorporated between the guide portion 305 and the fixed base 301, and joining and a complicated adjustment process are required. For this reason, the manufacture of the moving XY stage and the piezoelectric actuator 300 is complicated and difficult to adjust, and in order to increase the amount of movement of the movable table 303, a fulcrum is provided between the guide unit 305 and the fixed base 301 to provide an expansion displacement mechanism. There was a need. In addition, it is structurally difficult to cope with miniaturization. The present invention has been made to solve the above-described problems, and has been further devised from a new viewpoint.
[0006]
[Means for Solving the Problems]
In order to achieve the above-described object, a piezoelectric actuator according to the present invention forms a vibration member of a displacement mechanism unit that is flat and has one end fixed at the other end, and is provided with a piezoelectric element on the surface of the displacement mechanism unit. The displacement mechanism is configured to have a moving body that is supported or brought into contact with or supported by a support spring.
[0007]
When a frequency voltage is applied to the piezoelectric element provided in the flat displacement mechanism portion, the displacement mechanism portion bends and vibrates, and the free end of the displacement mechanism portion contacts the moving body. Since the free end of the displacement mechanism part performs an elliptical motion, this lateral component excites the movement of the moving body. In addition, since the moving body is supported by a support spring during the movement and the contact state between the displacement mechanism and the moving body is stably maintained, the moving body can be easily positioned and moved.
[0008]
In addition, the piezoelectric actuator according to the present invention is such that in the above piezoelectric actuator, the vibrating body is supported so as to face and follow the moving body surface. When the moving body changes its contact state with the vibrating body due to the roll during movement, the vibration of the displacement mechanism is efficiently transmitted by causing the vibrating body to follow the moving body surface against the roll. Like to do.
[0009]
In the piezoelectric actuator according to the present invention, the moving direction of the moving body is further restricted by the structure and configuration method of the spring portion that supports the moving body, and the moving direction of the moving body is restricted. It is what you do. By using a structure and construction method that weakens the spring constant for the moving direction of the moving body to give it a degree of freedom and increases the spring constant for displacement in other directions, the moving direction of the moving body and the stable Positioning can be performed.
[0010]
In the piezoelectric actuator according to the present invention, the piezoelectric actuator is further provided with a pressurizing unit that pressurizes and contacts the vibrating body and the moving body. By pressurizing the vibrating body and the moving body by the pressurizing means, the followability is further improved, and the contact state with the displacement mechanism section is improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the embodiments.
Embodiment 1 FIG.
1 is an assembly view showing a piezoelectric actuator according to Embodiment 1 of the present invention. The piezoelectric actuator 100 includes a first substrate 110 on which a movable stage 111 is formed and a second substrate 120 on which a vibrating body 121 is formed. The first substrate 110 has a structure in which the movable stage 111 is supported by four support springs 112. The support spring 112 has a serpentine shape, and the long side portion 112a has a small width, the short side portion 112b has a wide width, and is movable with the outer peripheral frame portion of the first substrate 110 connected to the support spring 112. The length to the stage 111 can be increased. The shape of the support spring 112 is not limited to a snake shape as shown in the figure, and may be any shape as long as the movable stage 111 can be moved without difficulty. The movable stage 111 has a guide protrusion 113 formed in the moving direction thereof. The guide protrusion 113 is engaged with the guide groove 114 and restricts the moving direction of the moving body 111. Depending on the structure of the support spring 112, the moving direction of the moving body 111 can be substantially restricted without the guide portions 113 and 114.
[0012]
For the first substrate 110, a stainless steel material or an aluminum material can be used. Further, a metallic or non-metallic elastic material such as beryllium copper, phosphor bronze, brass, duralumin, titanium or silicon can be used. The first substrate 110 can be processed by a photofabrication technique. This is because by using a non-machining process, it is possible to eliminate deformation, stress, and mechanical stress that occur during machining. In addition, by increasing the accuracy of the parts, the assembly process of each element part can be minimized, and the function and reproducibility are stabilized. In addition to the photofabrication technique, various processing methods such as wire electric discharge processing can be used. The aspect ratio of the support spring 112 is 1 or more, but this can be formed by a known negative tone near ultraviolet resist technique or the like.
[0013]
Further, it is preferable that a sliding surface (not shown) is provided at a portion of the lower surface of the moving body 111 that contacts the vibrating body 121. It is preferable to use a material that satisfies various conditions such as a large friction coefficient, excellent wear resistance, and a stable friction coefficient for the sliding surface. For example, the sliding surface can be formed by performing an oxide film treatment. The sliding surface may be made of cellulose fiber, carbon fiber, a composite material of whisker and phenol resin, or a composite material of polyimide resin and polyamide resin.
[0014]
The second substrate 120 has a structure in which a vibrating body 121 is formed in the center, and the vibrating body 121 is connected to the frame body 123 via an X-direction axis 122. Further, the frame is connected to the substrate part 125 via the Y-direction axis 124. Each axis is very narrow, and the torsional deformation can cause the vibrating body 121 to swing around the X axis and the Y axis. In addition, two L-shaped displacement mechanism portions 126 each having one end fixed at the other free end are opposed to each other in the X-axis direction (moving body traveling direction) of the vibrating body 120. A protrusion 127 for specifying a contact portion with the moving body 111 is formed at the tip of the displacement mechanism portion 126. The displacement mechanism 126 is not limited to an L shape, and may be a cantilever shape.
[0015]
FIG. 2 is a perspective explanatory view showing the back surface of the vibrating body of the second substrate shown in FIG. Each displacement mechanism 126 is joined with a piezoelectric element 128 that is polarized in a predetermined direction. The piezoelectric element 128 refers to a material having a strain generation function, a resonance function, and a voltage generation function. That is, it is a material that exhibits a characteristic in which stress or displacement is generated according to an applied voltage, a resonance phenomenon is generated according to the frequency of the applied voltage, and a voltage is generated according to an applied pressure. The piezoelectric element 128 of this example uses a thin film lead zirconate titanate having a high piezoelectric constant. Further, barium titanate, lithium niobate, lead zirconate titanate, or the like may be used. Further, functionally gradient materials and lithium niobate can be used instead of these piezoelectric ceramics. A driver for applying a frequency voltage is connected to the electrode of the piezoelectric element.
[0016]
The displacement mechanism 126 and the piezoelectric element 128 are integrated by bonding. The conditions required for such bonding are that the bonding layer is very thin, that the bonding layer is very hard and tough, and that the resistance value near the resonance frequency is after the displacement mechanism 126 and the piezoelectric element 128 are bonded. It is small. There is a bonding interface between the displacement mechanism 126 and the piezoelectric element 128 even when bonding is performed directly or by bonding with an adhesive. This bonding interface is an important factor that determines the propagation characteristics between the displacement mechanism 126 and the piezoelectric element 128. For this reason, the characteristics of the adhesive and the film thickness management are important. For example, a polymer adhesive represented by hot melt and epoxy resin is used as the adhesive. In this example, an optimum film thickness is obtained using an epoxy adhesive. Note that the piezoelectric element 128 may be directly bonded without using an adhesive. Further, the piezoelectric element may be provided by a thin film formation or pressure film formation process means.
[0017]
Further, the piezoelectric element 128 includes a unimorph type composed of one sheet, a bimorph type composed of two sheets, or a multimorph type composed of four or more sheets, and any of them may be used. The material of the piezoelectric element 128 and the displacement mechanism portion 126 and the bonding method thereof are set according to the displacement amount, force, response, and structural constraints of the displacement mechanism portion 126 required for the piezoelectric actuator. The displacement mechanism portion 126 of this example employs a unimorph type configuration. This is because it has a characteristic that it is difficult to have hysteresis in the displacement voltage characteristic. In addition, the displacement is small compared to the bimorph type, but the generated force is large, and the load and pressure applied to the moving body are appropriate. Depending on the specifications of the piezoelectric actuator, the displacement and force can be increased by adopting a multimorph type and increasing the number of layers while keeping the thickness constant. Further, a taper can be provided from the fixed end portion to the free end portion of the displacement mechanism portion 126 to improve the responsiveness. According to the vibrating body 121 having such a configuration, the bending displacement of the displacement mechanism portion 126 can be excited extremely stably.
[0018]
The second substrate 120 can also be integrally processed by photofabrication technology. The material of the second substrate 120 can be the same as that of the first substrate. In the above configuration, the vibrating body 120 is supported by the X-direction shaft 122, the frame body 123, and the Y-direction shaft 124. However, the present invention is not limited to this configuration, and any configuration can be used as long as the vibrating body 120 can be supported flexibly. May be. For example, as shown in FIG. 3A, 131 of the torsion shaft 1 and 132 of the torsion shaft 2 may be provided in the diagonal direction of the second substrate 120. Further, as shown in FIG. 5B, the vibrating body 121 may be supported by a torsion support spring 133 used for the first substrate 110. In this case, the vibrating body 121 can be pressed against the moving body 111 by the anti-torsion support spring 133 by delicate thickness control.
[0019]
Next, the operation principle of the piezoelectric actuator 100 will be described. FIG. 4 is an explanatory diagram showing the driving principle of the piezoelectric actuator of the present invention. When a specific voltage is applied to the electrode 129, the piezoelectric element 128 is bent toward the moving body 111 side. When voltage is applied, the piezoelectric element 128 returns to its original shape. When the piezoelectric element 128 is deformed, the displacement mechanism portion 126 is bent accordingly, and the free end tip of the displacement mechanism portion 126 generates an elliptical motion and comes into contact with the moving body 111. Therefore, the force of the lateral component at the tip of the free end (from right to left in the figure) is transmitted to the moving body 111 through the frictional force, and the moving body 111 moves slightly in the same direction. Accordingly, since the minute movement is repeated by periodically applying a voltage to the piezoelectric element 128, the moving body 111 can be continuously moved. In the figure, the contact portion between the displacement mechanism 126 and the moving body 111 is shown in a plane, but it is not always necessary to make a plane contact, and a point contact may be used.
[0020]
Next, the operation of the piezoelectric actuator 100 will be described. When a frequency voltage is applied to the piezoelectric element 128 of the displacement mechanism unit 126 facing in one direction, the moving body 111 moves according to the principle described above. Since the moving body 111 is supported by the support spring 112, the support spring 112 expands and contracts as the moving body 111 moves. In addition, since the moving body 111 is configured such that the moving direction thereof is regulated by the guide portions 113 and 114 and the direction in which the support spring 112 has a high degree of freedom coincides with the moving direction, the moving body 111 can reliably move in a desired linear manner. it can. Further, when a frequency voltage is applied to the piezoelectric element 128 of the displacement mechanism unit 126 facing in the reverse direction, the moving body 11 moves in the reverse direction.
[0021]
Further, in order to drive the moving body 111 stably, it is necessary that the facing surfaces of the vibrating body 121 and the moving body 111 maintain a uniform contact or interval. Since the vibrating body 121 is flexibly supported by the X-direction axis 122, the frame body 123, and the Y-direction axis 124, it is possible to follow a moving body surface that is slightly displaced, such as a roll or a pitch. For this reason, the moving body 111 can be stably controlled. Furthermore, if the pressure is applied, the vibrating body 121 and the moving body 111 are in a stable contact state, and stable driving is possible.
Embodiment 2. FIG.
FIG. 5 is an assembly diagram showing a piezoelectric actuator according to Embodiment 2 of the present invention. The piezoelectric actuator 200 is configured to be able to apply pressure to the vibrating body. The piezoelectric actuator 200 includes a first substrate 210 on which a moving body is formed, a second substrate 220 on which a vibrating body is formed, a pressurizing member 230 that applies pressure, a first spacer 240 that adjusts contact pressure, 1 substrate to a fixed substrate 250 on which the pressurizing member is placed, a second spacer 260 for adjusting the pressurization of the pressurizing member 230, and a holding substrate 270 for holding the first substrate to the pressurizing member.
[0022]
The first substrate 210 has a structure in which a moving body 211 is formed in the center, and the moving body 211 is supported by a support spring 212 with a degree of freedom set in the X direction. The support spring 212 has a structure in which rectangular frames are continuously connected at the center of the long side portion. In the support spring 212, the aspect ratio is increased by reducing the width of the rectangular frame and increasing the thickness thereof, thereby preventing torsional deformation. The first substrate 210 is not provided with a guide portion as in the first embodiment. This is because the structure of the support spring 212 substantially functions sufficiently as a guide portion. Since the structure of the second substrate 220 is the same as that of the first embodiment, the description thereof is omitted.
[0023]
The first spacer 240 adjusts the contact pressure between the vibrating body 221 and the moving body 211 formed on the second substrate 220. That is, by adjusting the distance between the displacement mechanism portion of the vibrating body 221 and the sliding surface of the moving body 211, the amount of displacement is adjusted (the lateral component of the contact force) so that optimum movement control can be performed. . The operating principle of the moving body 211 is as described above.
[0024]
The pressurizing member 230 has a configuration in which a cross-shaped through beam 232 is formed in the central hole 231. Protrusions 233 for pressing the vibrating body 221 are formed in the vicinity of both ends of the through beam 232, and the top portion thereof is the vibrating body 221. It contacts the lower surface of the. The amount of pressurization can be adjusted by the height of the protrusion 233 and the elastic force of the through beam 232. The shape of the pressurizing member 230 is not limited to that shown in the figure, and may be any shape as long as an appropriate pressurizing force can be applied to the vibrating body 211. For example, as shown in FIG. 6A, two beams 234 may be extended from both sides of the center hole 231, and a protrusion 235 may be provided at the tip of the beam to apply pressure. Further, as shown in FIG. 5B, the pressurizing unit 236 may be supported by a rectangular frame-shaped support spring 237.
[0025]
The second spacer 260 is disposed between the first substrate 210 and the second substrate 220 and manages the pressurization by this thickness. The first substrate 210, the second substrate 220, and the pressurizing member 230 are held on the fixing member 250 by the holding member 270. The first substrate 110 of the first embodiment can be used instead of the first substrate 210. Moreover, the number of displacement mechanism parts is not limited to four. What is necessary is just to determine according to a required driving force.
[0026]
Although not shown in the drawings, as a modification of the first and second embodiments, a displacement mechanism portion having two sizes of large and small sizes may be provided. According to this configuration, coarse movement control can be performed by a large displacement mechanism unit, and fine movement control can be performed by a small displacement mechanism unit.
[0027]
【The invention's effect】
As described above, according to the piezoelectric actuator of the present invention, since a piezoelectric element is provided in the shape of a flat plate-like displacement mechanism, process processing can be performed, a highly accurate shape can be obtained, and manufacture capable of mass reduction and cost reduction can be performed. . Functions of the shape and moving distance of the moving body can be realized according to desired specifications. Further, since the vibrating body follows the moving body, stable movement control is possible.
[0028]
Next, according to the piezoelectric actuator of the present invention, since the vibrating body is supported so as to follow and follow the surface of the moving body, stable movement control corresponding to the moving distance and the posture of the moving body is possible. Become.
Next, according to the piezoelectric actuator of the present invention, the moving direction of the moving body is regulated by the structure and the configuration method of the spring portion that supports the moving body, so that the moving body can be accurately detected with the minimum component configuration. It becomes possible to regulate the moving direction.
[0029]
Next, according to the piezoelectric actuator of the present invention, since the pressurizing means for pressurizing and contacting the vibrating body and the moving body is provided, further stable movement control can be performed.
[Brief description of the drawings]
FIG. 1 is an assembly diagram illustrating a piezoelectric actuator according to a first embodiment of the present invention.
FIG. 2 is a perspective explanatory view showing a back surface of a vibrating body of a second substrate shown in FIG.
FIG. 3 is an explanatory view showing a modification of a vibrating body.
FIG. 4 is an explanatory diagram showing the driving principle of the piezoelectric actuator of the present invention.
FIG. 5 is an assembly diagram showing a piezoelectric actuator according to a second embodiment of the present invention.
FIG. 6 is an explanatory view showing a modification of the pressurizing member.
FIG. 7 is a perspective view showing an example of a conventional piezoelectric actuator.
FIG. 8 is an enlarged plan view showing a support spring.
FIG. 9 is a structural explanatory view showing a support spring;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 100 Piezoelectric actuator 110 1st board | substrate 111 Movable stage 112 Support spring 113 Guide protrusion 114 Guide groove 120 2nd board | substrate 121 Vibrating body 122 X direction axis | shaft 123 Frame body 124 Y direction axis 125 Substrate part 126 Displacement mechanism part 127 Protrusion 128 Piezoelectric element 129 Electrode 131 Counter torsion shaft 1
132 Counter torsion shaft 2
133 Anti-torsion support spring 200 Piezoelectric actuator 210 First substrate 211 Moving body 220 Second substrate 221 Vibrating body 230 Pressurizing member 231 Central hole 232 Through beam 233 Protrusion 234 Beam 235 Protrusion 236 Pressing portion 237 Support spring 240 First spacer 250 Fixed substrate 260 Second spacer 300 Piezoelectric actuator 301 Fixed base 302 Extraction portion 303 Movable table 304 Support spring 304a Long side 304b Short side 305 Guide portion 306 Multilayer piezoelectric element

Claims (4)

A vibrating body, a displacement mechanism provided inside the vibrating body and having a free end that is freely movable with respect to the vibrating body, a fixed end fixed to the vibrating body, and one surface of the displacement mechanism In a piezoelectric actuator comprising: a piezoelectric element that moves the free end joined by bending thereof, and a moving body that contacts the other surface of the displacement mechanism part;
The moving body is supported by a support spring with respect to a first frame formed around the moving body, while the vibrating body is attached to a second frame formed around the vibrating body. On the other hand , the piezoelectric actuator is supported by a shaft-like member, and as a result, the movable body and the vibrating body swing so that their postures face each other and follow each other . A second substrate in which the movable body, the support spring, and the first frame body are integrally molded, and the vibration body, the shaft-shaped member, and the second frame body are integrally molded. The piezoelectric actuator according to claim 1, comprising a substrate . The moving body has a guide protrusion, and the first frame body has a guide groove that engages with the guide protrusion and restricts the moving direction of the moving body. The piezoelectric actuator according to claim 1 or 2. Furthermore, pressurizing means for applying a pressure to the vibrating body from the opposite surface of the vibrating body that contacts the moving body so that a contact pressure between the vibrating body and the moving body is enhanced. The piezoelectric actuator according to claim 1, wherein the piezoelectric actuator is provided.

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