JP2011185399A - Turbulent flow control device and method for manufacturing actuator for turbulent flow control - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turbulent flow control device using an actuator which can simplify manufacturing processes and achieve high stroke output by low-voltage drive. <P>SOLUTION: The turbulent flow control device installed to a wall forming a boundary surface with fluid, includes a diaphragm type piezoelectric actuator (20) group constituted by laminating a first electrode (40), a piezoelectric membrane (44), and a second electrode (46) on a surface of a diaphragm (30). By applying voltage to between the first electrode (40) and the second electrode (46), a movable part (32) is displaced to deform the boundary surface with the fluid and thereby to control wall turbulence. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a turbulent flow control device suitable for controlling turbulent flow generated in the vicinity of a surface (wall surface) of an object and a technique of a manufacturing method of a turbulent flow control actuator used therefor.

  By controlling the turbulent flow that occurs as a natural phenomenon, it is possible to reduce fluid resistance, increase or suppress heat transfer, or control mixing and diffusion of multiple types of fluids. From the viewpoint of reducing environmental impact, etc. Development of control technology is expected (see Non-Patent Document 1).

  Conventionally, attempts have been made to control turbulence by devising the surface shape and surface properties of the wall, such as the addition of a wall having a structure similar to shark skin or a surfactant. For example, Patent Document 1 proposes a method in which a large number of V-shaped protrusions are arranged on the wall surface, and turbulence is reduced or increased by the shape and arrangement pattern of the V-shaped elements.

  However, since the turbulent flow changes according to the state of the flow from moment to moment, ideal turbulent flow control senses the state of turbulent flow in real time and moves the actuators accordingly, It is to give feedback.

  In recent years, MEMS (Micro Electro Mechanical System) technology applying a semiconductor process has been greatly developed, and research on turbulent flow control using a sensor and an actuator manufactured by the MEMS technology has been performed (Non-patent Document 1).

  The specifications desired for the actuator used for such turbulent flow control vary depending on the Reynolds number of the fluid to be controlled, but generally have dimensions of 100 μm to several mm, high stroke, operating frequency of 100 Hz to 100 kHz, and usage environment. High durability and low power consumption. In response to such required specifications, conventional turbulent flow control MEMS actuators include electromagnetic and dielectric elastomers (Patent Document 2, Non-Patent Document 1).

Yuji Suzuki, Nobuhide Kasaki, “Wall turbulent feedback control using MEMS devices”, Nagare, Journal of Japan Hydrodynamic Society, Vol. 25, April 2006, pp. 95-102 (2006).

Japanese Patent Laid-Open No. 10-183557 Japanese Patent No. 2862855

  However, the conventionally proposed electromagnetic actuator can output a high torque, but it is difficult to manufacture because of its complicated structure, and has problems such as crosstalk and high power consumption. On the other hand, the dielectric elastomer can give a high displacement, but it is necessary to apply a voltage on the order of kV, and problems remain in terms of the load on the drive circuit of the electric system and safety.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a turbulent flow control device using an actuator capable of simplifying a manufacturing process and capable of high stroke output by low voltage driving, In addition, an object of the present invention is to provide an actuator manufacturing method applied to the turbulent flow control device.

  In order to achieve the above object, the following invention modes are provided.

  (Invention 1): A turbulent flow control device according to Invention 1 is a turbulent flow control device installed on a wall that forms a boundary surface with a fluid, and includes a first electrode, a piezoelectric film, A diaphragm type piezoelectric actuator group formed by laminating a second electrode is provided, and the boundary surface includes a surface of a movable part of the diaphragm type piezoelectric actuator group, and a voltage between the first electrode and the second electrode is formed. The movable portion is displaced by application to deform the boundary surface.

  According to the present invention, by using a diaphragm type piezoelectric actuator using a piezoelectric film, it is possible to drive at a lower voltage as compared with a configuration using a conventional electromagnetic type or dielectric elastomer. Thereby, power consumption can be reduced. In addition, the turbulent flow control device of the present invention can achieve the simplification of the manufacturing process by applying the thin film technology (film formation technology) and the MEMS technology, and can improve the yield and reduce the cost.

  (Invention 2) The turbulent flow control device according to Invention 2 is characterized in that, in Invention 1, the piezoelectric film has an absolute value of a piezoelectric constant d31 of 200 pm / V or more.

  By using a piezoelectric film having an absolute value of the piezoelectric constant d31 of 200 pm / V or more, it is possible to realize a piezoelectric actuator capable of outputting a high stroke while being a thin film. The piezoelectric constant d31 usually has a negative sign. This means that when a voltage is applied in the film thickness direction, the film shrinks in the in-plane direction.

  (Invention 3): The turbulent flow control device according to Invention 3 is provided with a structure having a cavity corresponding to a region of the movable portion of the diaphragm according to Invention 1 or 2, wherein the diaphragm has an opening surface of the cavity. And is joined to the structure.

  According to this aspect, a diaphragm structure can be formed.

  (Invention 4): The turbulent flow control device according to Invention 4 is characterized in that, in Invention 3, the cavity has a circular opening in plan view.

  According to this aspect, deterioration and breakage due to stress concentration can be reduced, and a highly reliable actuator can be provided.

  (Invention 5): The turbulent flow control device according to Invention 5 is characterized in that, in Invention 3 or 4, the second electrode includes a ring-shaped or C-shaped electrode.

  According to this aspect, it is possible to deform the wall surface into a convex shape.

  (Invention 6): The turbulent flow control device according to Invention 6 according to Invention 5, wherein the ring-shaped or C-shaped electrode is formed along the opening circle of the cavity in plan view, and the ring-shaped Alternatively, a part of the C-shaped electrode protrudes outside the opening circle of the cavity in a plan view.

  According to such an embodiment, a part of the piezoelectric film under the electrode is restrained by the structure, and the unconstrained portion of the diaphragm can be greatly displaced.

  (Invention 7): The turbulent flow control device according to Invention 7 includes, in Invention 4, a circular electrode as the second electrode, and the diameter of the circular electrode is 50 to 75% of the opening diameter of the cavity. And is formed inside the opening circle of the cavity in plan view.

  According to this aspect, an actuator having excellent durability can be realized, and a large displacement amount suitable for turbulent flow control can be obtained.

  (Invention 8): The turbulent flow control device according to Invention 8 is characterized in that, in any one of Inventions 1 to 7, the piezoelectric film is a perovskite ferroelectric.

  (Invention 9): The turbulent flow control device according to Invention 9, in any one of Inventions 1 to 8, outputs a drive signal for driving each actuator of the diaphragm type piezoelectric actuator group at a resonance frequency of the diaphragm structure. A drive control circuit is provided.

  A larger displacement can be obtained by utilizing the resonance of the diaphragm.

  (Invention 10): The turbulent flow control device according to Invention 10 is disposed in an upstream side of the flow of the fluid with respect to the arrangement position of the diaphragm type piezoelectric actuator group in any one of Inventions 1 to 9, and the fluid And a control circuit for controlling the driving of the diaphragm type piezoelectric actuator group based on information obtained from the sensor group.

  According to this aspect, it is possible to provide a system capable of appropriate turbulent flow control corresponding to the fluid flow situation that changes from moment to moment.

  (Invention 11): A turbulent flow control actuator manufacturing method according to invention 11 is a turbulent flow control actuator constituting the diaphragm type piezoelectric actuator group in the turbulent flow control device according to any one of inventions 1 to 10. And a step of forming a cavity on one side of the first substrate, a step of bonding the second substrate to the first substrate so as to cover the opening surface of the cavity, and a step of bonding to the first substrate. A step of thinning the second substrate and forming a diaphragm with the remainder, a step of forming a first electrode, a piezoelectric film, and a second electrode on the diaphragm in this order; and the second The method includes a step of removing a part of the electrode and patterning it into a predetermined electrode shape, and a step of removing a part of the piezoelectric film and patterning it into a predetermined piezoelectric body shape.

  The actuator group using the piezoelectric film according to the present invention can be driven at a low voltage as compared with a configuration using a conventional electromagnetic type or dielectric elastomer, and can reduce power consumption. In addition, the turbulent flow control device of the present invention can achieve a simplification of the manufacturing process by using a thin film deposition technique and a MEMS technique, leading to yield improvement and cost reduction.

The top view of the boundary layer control apparatus which concerns on 1st Embodiment of this invention. It is an enlarged view of the actuator shown in FIG. 1, (a) is a top view, (b) is sectional drawing. The block diagram which showed the system configuration | structure of the turbulent flow control apparatus which concerns on this embodiment Process chart showing an example of actuator array manufacturing process The enlarged view of the actuator which shows 2nd Embodiment of this invention The enlarged view of the actuator which shows 3rd Embodiment of this invention

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<First Embodiment>
FIG. 1 is a plan view of a boundary layer control apparatus according to the first embodiment of the present invention. The turbulent flow control device 10 of this example includes an actuator group 21 in which a plurality of piezoelectric thin film diaphragm type MEMS actuators 20 are arranged on a wall surface 12 in contact with a fluid. Hereinafter, reference numeral 20 is simply referred to as “actuator”, and the entire actuator group is indicated by reference numeral 21. Here, for simplicity of explanation, the wall surface 12 is a substantially flat plane, but the wall surface 12 may be a wall surface (curved surface) having a curvature when the present invention is implemented.

  The fluid may be either gas or liquid. It is assumed that the fluid flows on the wall surface 12 provided with the actuator group 21 from the left to the right in FIG. For convenience of explanation, the fluid flow direction is the x direction, the direction orthogonal to the x direction and parallel to the wall surface 12 (vertical direction in FIG. 1) is the z direction, the normal direction of the wall surface 12 (the direction away from the wall surface, FIG. The coordinate system is defined with the y direction as the direction toward the front of the page.

  In the actuator group 21 of this example, actuator rows in which the actuators 20 are arranged at a constant interval Lz along the z direction are provided in a plurality of rows (here, three rows are illustrated) at a constant interval Lx in the x direction. It has been.

  Here, an example is shown in which the actuators 20 are two-dimensionally arranged in a matrix, but the arrangement form of the actuators 20 is not limited to this example. For example, the actuator interval in the z direction in the actuator row may be Lz (constant), and the actuator rows having different positions in the x direction may be shifted in the z direction. For example, the positions may be shifted in the z direction by Lz / 2 between adjacent actuator rows to form a staggered arrangement.

  2 is an enlarged view of one actuator 20, FIG. 2 (a) is a plan view, and FIG. 2 (b) is a cross-sectional view thereof (cross-sectional view taken along line 2b-2b in FIG. 2 (a)). It is. As shown in these drawings, the actuator 20 has an opening surface (upper surface in FIG. 3) of the recess 23 on a substrate 26 (corresponding to a “structure”) on which the recess 23 constituting the cavity 22 is formed. The diaphragm 30 is joined so as to cover it, and the lower electrode 40, the piezoelectric film 44, and the upper electrode 46 are patterned on the diaphragm 30.

  In FIG. 2, reference numeral 47 is a wiring lead electrode connected to the upper electrode 46 of each actuator 20. The wiring lead-out electrode 47 is connected to the pattern of the wiring line 48 (see FIG. 1). As shown in FIG. 1, in the actuator array of this example, the wiring line 48 of each actuator 20 is drawn out in the z direction for each actuator row 24 along the z direction. Although not shown in the drawing, the wiring line 48 is connected to the drive circuit. The actuator 20 is activated by applying a drive voltage to each actuator 20 through the wiring line 48. Each actuator 20 can be driven and controlled individually, or can be driven and controlled in units of columns.

  As shown in FIG. 2A, the cavity 22 is circular in plan view. In the diaphragm 30 for sealing the upper surface of the cavity 22, the inner region of the opening circle of the cavity 22 (broken line circle in FIG. 2A) is not constrained by the substrate 26, and the unconstrained region is substantially the same. This is a movable part (reference numeral 32 in FIG. 2B) that is displaceable. On the other hand, a diaphragm 30 is joined (restrained) to the upper surface of the substrate 26 outside the cavity 22 (see FIG. 2B), and the restrained portion is configured to support the diaphragm 30. In the actuator 20 having such a diaphragm structure, a non-restraining region (movable portion 32) having the edge of the cavity 22 as a boundary is displaced. Therefore, from the viewpoint of avoiding deterioration or destruction due to stress concentration, the opening shape of the cavity 22 is preferably circular rather than rectangular.

  The lower electrode 40 of the present example uniformly covers the upper surface of the diaphragm 30 and is a common electrode for the plurality of actuators 20, but matches the shape of the actuator 20 (for example, the piezoelectric film 44 According to the pattern), it may be patterned.

  The piezoelectric film 44 is patterned in a ring shape along the outer periphery of the cavity 22 in plan view. The outer diameter of the ring-type piezoelectric film 44 is larger than the diameter of the cavity 22 and protrudes outside the opening circle of the cavity 22. The inner diameter of the ring-type piezoelectric film 44 is smaller than the diameter of the cavity 22, and the inner peripheral edge of the piezoelectric film 44 is inside the opening circle of the cavity 22.

  The upper electrode 46 is formed in a ring shape concentrically with the piezoelectric film 44 on the ring-type piezoelectric film 44. The outer diameter of the ring-shaped upper electrode 46 is smaller than the outer diameter of the piezoelectric film 44, but larger than the diameter of the cavity 22 and protrudes outside the opening circle of the cavity 22. The inner diameter of the upper electrode 46 is larger than the inner diameter of the piezoelectric film 44, but smaller than the diameter of the cavity 22, and the inner peripheral edge of the upper electrode 46 is inside the opening circle of the cavity 22.

That is, the radius of the opening circle of the cavity 22 is r ₀ , the outer peripheral radius of the ring-type piezoelectric film 44 is r ₁ , the inner peripheral radius is r ₂ , the outer peripheral radius of the upper electrode 46 is r ₃ , and the inner peripheral radius is r ₄ . Then, these are common in the center (concentric), and satisfy the relationship r ₂ <r ₄ <r ₀ <r ₃ <r ₁ .

  On the lower electrode 40, not only the ring-type piezoelectric film 44 but also piezoelectric films functioning as support layers 52 and 53 for supporting the wiring electrodes (47 and 48) are formed.

  When a driving voltage is applied to the piezoelectric thin film element having such a ring-type piezoelectric film 44 and the upper electrode 46, the piezoelectric film 44 sandwiched between the electrodes contracts in the d31 direction, and is on the cavity 22. The diaphragm 30 portion (movable portion 32) is displaced upward in FIG.

  In FIG. 2B, in order to visually emphasize each layer, it is drawn at a ratio different from the actual film thickness ratio. As an example of the implementation dimensions, the film thickness of the piezoelectric film 44 is 2 to 3 μm, and the film thickness of the upper electrode 46 is 0.2 μm. The surface unevenness due to the laminated structure of the piezoelectric film 44 and the upper electrode 46 is extremely small (small enough to be ignored) with respect to the surface of the lower electrode 40, and becomes a substantially flat wall surface 12 in the non-driven state. Yes. And the displacement amount of the movable part 32 by the piezoelectric drive in the y direction is on the order of 10 μm to 100 μm.

  Thus, the boundary surface with the fluid is formed including the surface of the movable portion 32 of the actuator 20, and the boundary surface is directly deformed by driving the actuator 20 to control the flow of the boundary layer.

  FIG. 3 is a block diagram showing a system configuration of the turbulent flow control device 10 according to the present embodiment. A plurality of actuators 20 are arranged on the wall surface 12, and the sensor 70 is arranged on the wall surface 12 on the upstream side of the fluid flow from the arrangement position of the actuator group 21. Although only one sensor 70 is shown in FIG. 3, the sensor 70 is provided as a sensor group (sensor array) arranged on the wall surface 12 along the z direction, like the actuator row 24 in FIG. 1. It has been.

  Although the detailed configuration of the sensor 70 is not shown, various forms such as a means for detecting wall pressure, a means for detecting wall shear stress, and a means for detecting wall temperature can be employed (see Non-Patent Document 1). ). In the present embodiment, a hot film shear stress sensor is used that embeds a heater in the wall surface 12 and obtains flow information on the wall surface using the correlation between the amount of heat lost to the fluid and the shear stress.

  The control unit 80 is a control unit that obtains information from the sensor 70 and controls the operation of the actuator 20. The control unit 80 includes a driving circuit for the sensor 70, a signal processing circuit for processing a signal from the sensor 70, an arithmetic circuit for calculating the control amount of the actuator 20, a control circuit for generating a control signal based on the calculation result, and the actuator 20 A drive circuit (for example, a power amplifier) for driving is included. The control unit 80 calculates the control amount of the actuator 20 based on information obtained from the sensor 70, and generates a control signal for the actuator 20 according to the calculation result. Based on this control signal, a drive signal for the actuator 20 is output. That is, the control unit 80 of this example serves as a “drive circuit”, “control circuit”, and “drive control circuit”.

  1 to 3, the sensor 70 group on the wall surface 12 senses a turbulent state upstream of the fluid, and the driving voltage of each downstream actuator 20 is determined based on the information. The The determined drive voltage signal (drive signal) is supplied to each actuator 20. When a voltage is applied to the actuator 20, the diaphragm on the cavity 22 warps in a convex direction (upward direction in FIG. 3) in the fluid advancing layer. The displacement of the actuator 20 affects the boundary layer and controls the fluid. The control mode is not limited to the control for suppressing turbulent flow, and control for increasing turbulent flow is also possible.

  According to the present embodiment, the actuator 20 at a necessary position can be displaced by a necessary amount in accordance with the fluid flow state (wall turbulent state). As a result, the boundary surface with the fluid can be actively deformed, and the flow of the boundary layer can be adaptively controlled.

<Manufacturing method of actuator array>
Next, an example of a method for manufacturing a piezoelectric thin film diaphragm type MEMS actuator array will be described. FIG. 4 is a process diagram of a manufacturing process suitable for manufacturing the actuator array described with reference to FIGS.

  (Step 1): As shown in FIG. 4A, first, a silicon (Si) wafer substrate 100 (corresponding to a “first substrate”) is prepared.

  (Step 2): Next, a cavity 102 having a depth of about 50 μm is formed on the silicon wafer substrate 100 by dry etching using the Bosch method (FIG. 4B). The cavity 102 corresponds to the cavity 22 described with reference to FIGS. Here, the diameter φD0 of the cavity 102 is set to φ3 mm.

  (Step 3): Next, the device layer 114 side of a separately prepared SOI (silicon on insulator) substrate 110 (corresponding to “second substrate”) and the cavity surface of the silicon wafer substrate 100 are bonded (FIG. 4C). )). In this bonding step, annealing is performed at a high temperature, and the bonding is strengthened by diffusion bonding. The device layer 114 of the SOI substrate 110 is desirably about 3 to 5 μm thick.

(Step 4): Next, the handle layer 118 of the SOI substrate 110 is removed by polishing and dry etching (FIG. 4D). At this time, the SiO ₂ layer 116 functions as an etching stopper layer. The handle layer 118 and the SiO ₂ layer 116 are removed, and the remainder after the thinning, that is, the device layer 114 forms the diaphragm 30 (see FIG. 2).

In the present example, to remove the SiO ₂ layer 116, leaving the SiO ₂ layer 116, may form a "diaphragm" by the stack of the SiO ₂ layer 116 and the device layer 114.

(Step 5): Next, as shown in FIG. 4E, on the device layer 114, a lower electrode (Ti (10 nm) / Pt (200 nm)) 120, a piezoelectric film (2um) 132, an upper part Electrodes (Ti (10 nm) / Au (200 nm) 146 are formed in this order by sputtering. The piezoelectric film 132 formed at this time is composed of lead zirconate titanate (PZT: general formula Pb (Zr _x It was a Ti _1-x ) O ₃ (0 <x <1))-based piezoelectric film (PZT film), and its piezoelectric constant was d 31 = −250 pm / V.

  The piezoelectric film 132 is preferably formed directly on the structure by a sputtering method, a chemical vapor deposition method (CVD), a sol-gel method, or the like from the viewpoints of mass productivity, yield improvement, and performance variation of a completed device. In particular, a sputtering method that can form a low-temperature film for reducing thermal stress and can form a thick film with a large driving torque of several μm or more is desirable.

  The lower electrode 120 of the present example has a layer structure in which a titanium (Ti) film having a thickness of 10 nm and a platinum (Pt) film having a thickness of 200 nm are stacked thereon from the device layer 114 side. In FIG. 4E, the laminated electrodes are collectively shown as a “lower electrode 120”. Similarly, the upper electrode 146 is composed of a laminated structure of a titanium Ti film (10 nm thickness) and a gold Au film (200 nm thickness) (the piezoelectric film 132 side is a Ti film). In FIG. The electrodes are collectively shown as “upper electrode 146”.

  (Step 6): Next, the upper electrode 146 is patterned by lithography and etching (wet etching or dry etching) (FIG. 4F). By this upper electrode patterning step, the ring-type upper electrode 46 and wiring electrodes (47, 48) shown in FIGS. 1 to 2 are formed.

  (Step 7): Next, after lithography, the piezoelectric film 132 is etched and patterned by dry etching (FIG. 4G). This ring-patterned pattern described in FIGS. The patterns of the support layers 52 and 53 of the piezoelectric film 44 and the wiring electrodes (47 and 48) are formed.

  The actuator 20 demonstrated in FIGS. 1-3 is obtained by the above-mentioned processes 1-7.

<Displacement experiment>
When a voltage of 50 V was applied to the actuator 20 obtained by the manufacturing process described in FIG. 4, a convex displacement of 12 μm was obtained. Furthermore, by driving the actuator 20 at the resonance frequency of the actuator 20 (diaphragm resonance frequency), a displacement of 150 μm was obtained.

  This amount of displacement is sufficient for an actuator for boundary layer control in automobiles, small aircraft, and the like. As the drive signal generation means in the control unit 80 described with reference to FIG. 3, it is preferable to include a drive control circuit that outputs a signal having a waveform for driving the actuator 20 at a frequency equivalent to the resonance frequency of the actuator 20.

  As one of the backgrounds for realizing such a high-displacement piezoelectric film actuator, there is a film forming technique that can form a piezoelectric film having a high piezoelectric constant (the absolute value of d31 is 200 pm / V or more). There is an improvement. In the present embodiment described with reference to FIGS. 1 to 4, in order to further maximize the amount of displacement, the surrounding piezoelectric film is removed by pattern etching to reduce restraint, and the upper electrode 46 with respect to the chamber (cavity 22). The size is optimized. Thus, a piezoelectric film actuator capable of obtaining a displacement suitable for controlling the boundary layer has been achieved.

<Advantages of using piezoelectric thin film>
The piezoelectric film has advantages such as low power consumption, high torque, and low voltage driving, and is a preferable driving method for a turbulent flow control MEMS actuator. Conventional thin-film piezoelectric materials have a weakness in that the piezoelectric constant is inferior to that of fired bulk piezoelectric materials, but in recent years, high-piezoelectric constant thin-film piezoelectric materials have been developed. An actuator capable of stroke output can be manufactured. An actuator formed of a piezoelectric thin film has an advantage that there is little resistance in the fluid because there are few structural irregularities on the outermost surface. Furthermore, the piezoelectric thin film has an advantage that it can be formed on an arbitrary streamlined surface by using a film forming method such as sputtering.

Second Embodiment
Next, a second embodiment of the present invention will be described. Although the actuator 20 having the ring-shaped upper electrode 46 has been described in the first embodiment, an actuator 220 having a circular upper electrode 246 as shown in FIG. 5 may be used instead. In FIG. 5, the same or similar elements as those described in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted.

5A is a plan view, and FIG. 5B is a cross-sectional view (a cross-sectional view taken along line 5b-5b in FIG. 5A). In FIG. 5, reference numeral 244 denotes a piezoelectric film, 246 denotes an upper electrode, and 247 denotes a wiring electrode. The actuator 220 has a circular upper electrode 246 (radius r ₃ <r ₀ ) on a circular piezoelectric film 244 (radius r ₁ > r ₀ ) larger than the opening circle (radius r ₀ ) of the cavity 22. They are stacked.

The displacement direction of the actuator 220 when the drive voltage is applied is a direction indented inside the cavity 22 (a direction in which the wall surface 12 is dented). That is, the piezoelectric body under the upper electrode 246 contracts in the d31 direction, and the diaphragm is recessed in the cavity 22. Therefore, compared with the case where the ring-type actuator 20 described in the first embodiment moves in the convex direction, the degree of influence on the boundary layer is low, but the displacement is 10% to 30% larger than that of the ring-type actuator. Further, the actuator 220 in FIG. 5 is durable because no voltage is applied to the piezoelectric film (region of r ₀ <r <r ₁ ) in the constrained portion of the piezoelectric film 244 that is constrained (supported) by the substrate 26. From the standpoint of performance, this is a more desirable form than the ring-type actuator 20 according to the first embodiment.

In the configuration of FIG. 5, in order to maximize the amount of displacement in the recess direction, the diameter (2 × r ₃ ) of the circular upper electrode 246 is 50% to 75% of the diameter (2 × r ₀ ) of the cavity 22. It is good to be about%.

<Third Embodiment>
Next, a third embodiment of the present invention will be described.

  In order to achieve a further increase in displacement, the ring-type electrode (reference numeral 46) described in the first embodiment and the circular electrode (reference numeral 246) described in the second embodiment are combined. An embodiment for producing an actuator is also possible. An example is shown in FIG. In FIG. 6, the same or similar elements as those described in FIGS. 2 and 5 are denoted by the same reference numerals, and the description thereof is omitted.

  6A is a plan view, and FIG. 6B is a cross-sectional view (a cross-sectional view taken along line 6b-6b in FIG. 6A). In FIG. 6, reference numeral 346 denotes a C-type upper electrode provided in place of the ring-type electrode (46) described in FIG. Reference numeral 47 in FIG. 6 is a wiring electrode connected to the C-type upper electrode 346, and reference numeral 247 is a wiring electrode connected to the circular upper electrode 246.

  A wiring electrode 247 is formed at a notch in the C-type upper electrode 346, and independent voltages can be applied to the circular upper electrode 246 and the surrounding C-type upper electrode 346, respectively. It has become. According to the actuator 320 having such a structure, the displacement amount (stroke) can be further increased.

  As a manufacturing method of the actuator 320 shown in FIG. 6, a method similar to the process (FIG. 4) described in the first embodiment can be applied.

  In place of the ring-type upper electrode 46 described with reference to FIGS. 1 and 2, an actuator employing a C-type upper electrode 346 may be used.

<About the composition of the piezoelectric film>
As a piezoelectric film that can be used in the practice of the present invention, a piezoelectric film made of one or more perovskite oxides represented by the following general formula (P) (may contain unavoidable impurities) Is mentioned. Such a piezoelectric film can be formed on the substrate by a sputtering method using plasma.

General formula A _a B _b O ₃ (P)
In the formula, A is an A site element containing Pb as a main component, B is an element of a B site, and Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Sc, Co, Cu, In, At least one element selected from the group consisting of Sn, Ga, Zn, Cd, Fe, and Ni, O is oxygen is typically a ≧ 1.0 and b = 1.0, These numerical values may deviate from 1.0 within a range where a perovskite structure can be taken.

  Examples of the perovskite oxide represented by the general formula (P) include lead titanate, lead zirconate titanate (PZT), lead zirconate, and lead niobate zirconium titanate. The piezoelectric film may be a mixed crystal system of perovskite oxides represented by the above general formula (P).

  In carrying out the present invention, in particular, a piezoelectric film composed of one or more perovskite oxides (which may contain inevitable impurities) represented by the following general formula (P-1). More preferred.

Pb _a (Zr _b1 Ti _b2 X _b3 ) O ₃ (P-1)
In formula (P-1), X is at least one metal element selected from the group of elements of group V and group VI. a> 0, b1> 0, b2> 0, b3 ≧ 0. Although it is standard that a ≧ 1.0 and b1 + b2 + b3 = 1.0, these numerical values may deviate from 1.0 within a range where a perovskite structure can be taken.

  The perovskite oxide represented by the general formula (P-1) is lead zirconate titanate (PZT) when b3 = 0, and when b3> 0, part of the B site of PZT is group V. And an oxide substituted with X which is at least one metal element selected from the group of elements of group VI.

  X may be any metal element of Group VA, Group VB, Group VIA, and Group VIB, and is preferably at least one selected from the group consisting of V, Nb, Ta, Cr, Mo, and W. .

  Since the piezoelectric film made of the perovskite oxide represented by the general formulas (P) and (P-1) has a high piezoelectric strain constant (d31 constant), a piezoelectric actuator (actuator) including the piezoelectric film is provided. The element is excellent in displacement characteristics. In particular, in the perovskite oxides represented by the general formulas (P) and (P-1), good characteristics are obtained when the composition a of Pb is in the range of 1.02 <a ≦ 1.3. It is done.

<Modification 1>
The implementation of the present invention is not limited to the piezoelectric material, electrode material, film formation conditions, film thickness dimensions, drive voltage, and other conditions in the above-described embodiments, and can be performed under various conditions. is there. In addition, an SOI substrate can be used instead of the silicon wafer substrate 100.

<Modification 2>
In FIG. 1, the actuator group 21 in which a large number of actuators 20 having the same size and the same shape are arranged has been described. However, a plurality of types of actuators having different sizes and displacement amounts may be combined. For example, a control mode may be employed in which a large actuator (with a large displacement) is operated for a large turbulent flow and a small actuator is operated for a small turbulent flow. However, the system can be configured more simply by arranging the same actuators.

<Modification 3>
In FIG. 1, the actuator group 21 in which the actuators 20 are two-dimensionally arranged has been described. However, even in a one-dimensional arrangement (for example, the actuators 20 arranged in a line along the z direction) A control effect is obtained. However, in order to realize more effective turbulent flow control, a mode in which a plurality of actuators are arranged at different positions in the x direction and the z direction (two-dimensionally arranged mode) is preferable.

<Modification 4>
In the second embodiment described with reference to FIG. 5, the structure in which the lower electrode 40, the piezoelectric film 244, and the upper electrode 246 are stacked on the upper surface of the vibration plate 30 in FIG. 5 has been described. A configuration in which a lower electrode, a piezoelectric film, and an upper electrode are stacked on the lower surface (cavity 22 side) is also possible. In this case, the manufacturing process is somewhat complicated, but displacement in the convex direction with respect to the wall surface 12 is possible.

  DESCRIPTION OF SYMBOLS 10 ... Turbulence control apparatus, 12 ... Wall surface, 20 ... Actuator, 21 ... Actuator group, 22 ... Cavity, 26 ... Substrate, 30 ... Vibration plate, 32 ... Movable part, 40 ... Lower electrode, 44 ... Piezoelectric film, 46 ... Upper electrode, 70 ... Sensor, 80 ... Control unit, 100 ... Silicon wafer substrate, 110 ... SOI substrate, 102 ... Cavity, 120 ... Lower electrode, 132 ... Piezoelectric film, 146 ... Upper electrode, 220, 320 ... Actuator, 244: Piezoelectric film, 246, 346: Upper electrode

Claims (11)

A turbulence control device installed on a wall that forms a boundary surface with a fluid,
A diaphragm type piezoelectric actuator group in which a first electrode, a piezoelectric film and a second electrode are laminated on the surface of the diaphragm,
The boundary surface includes a surface of a movable part of the diaphragm type piezoelectric actuator group,
A turbulent flow control device configured to deform the boundary surface by displacing the movable portion by applying a voltage between the first electrode and the second electrode. In claim 1,
The piezoelectric film has a piezoelectric constant d31 having an absolute value of 200 pm / V or more. In claim 1 or 2,
Comprising a structure having a cavity corresponding to the region of the movable part of the diaphragm;
The turbulent flow control device according to claim 1, wherein the diaphragm is bonded to the structure so as to cover an opening surface of the cavity. In claim 3,
The turbulent flow control device, wherein the cavity has a circular opening in a plan view. In claim 3 or 4,
A turbulent flow control device comprising a ring-shaped or C-shaped electrode as the second electrode. In claim 5,
The ring-shaped or C-shaped electrode is formed along the opening circle of the cavity in plan view, and a part of the ring-shaped or C-shaped electrode is opened in the cavity in plan view. A turbulent flow control device characterized by projecting outward from a circle. In claim 4,
As the second electrode, a circular electrode is provided, and the diameter of the circular electrode is in the range of 50 to 75% of the opening diameter of the cavity, and is formed inside the opening circle of the cavity in plan view. A turbulent flow control device. In any one of Claims 1 thru | or 7,
2. The turbulent flow control device according to claim 1, wherein the piezoelectric film is a perovskite ferroelectric. In any one of Claims 1 thru | or 8,
A turbulent flow control device comprising a drive control circuit for outputting a drive signal for driving each actuator of the diaphragm type piezoelectric actuator group at a resonance frequency of the diaphragm structure. In any one of Claims 1 thru | or 9,
A sensor group that is disposed upstream of the fluid flow with respect to the position of the diaphragm type piezoelectric actuator group, and that detects a state of the fluid flow;
A control circuit for controlling the driving of the diaphragm type piezoelectric actuator group based on information obtained from the sensor group;
A turbulent flow control device comprising: A method for manufacturing an actuator for turbulent flow control constituting the diaphragm type piezoelectric actuator group in the turbulent flow control device according to any one of claims 1 to 10,
Forming a cavity on one side of the first substrate;
Bonding a second substrate to the first substrate so as to cover an opening surface of the cavity;
Thinning the second substrate bonded to the first substrate, and forming a diaphragm with the remainder;
Forming a first electrode, a piezoelectric film, and a second electrode in this order on the diaphragm;
Removing a portion of the second electrode and patterning it into a predetermined electrode shape;
Removing a part of the piezoelectric film and patterning the piezoelectric film into a predetermined shape;
A method of manufacturing an actuator for controlling turbulent flow, comprising:

Images