TW201436447A - Piezoelectric converter and flow sensor in which same is used - Google Patents

Abstract

In the present invention, a piezoelectric converter is provided with a supporting section, a facing section, and an oscillation block. The oscillation block is present between the supporting section and the facing section, and has one edge fixed to the supporting section and the other edge set apart from the facing section. The oscillation block is provided with a beam section, a weight section, a protrusion section, and a piezoelectric conversion section. The beam section is thinner than the supporting section, and is swingably supported by the supporting section. The weight section is provided at the front edge of the beam section, and is thicker than the beam section. The protrusion section protrudes toward the opposite side of the weight section to the beam section side, and is thinner than the weight section and the facing section. The piezoelectric conversion section generates an AC voltage in accordance with the oscillation of the beam section. The oscillation block is bent so as to prevent a normal to the front edge surface of the protrusion section from intersecting the facing section.

Description

Piezoelectric conversion device and flow sensor using the same

The present invention relates to a piezoelectric conversion device and a flow sensor using the same.

In the piezoelectric conversion device, for example, a power generating device having the configuration shown in FIG. 20A and FIG. 20B has been proposed (for example, refer to Japanese Patent Laid-Open Publication No. 2011-91977). Japanese Patent Publication No. 2011-91977 is referred to as Document 1.

The power generating device includes: a cantilever beam forming substrate 120; and a piezoelectric conversion portion 124. The piezoelectric conversion portion 124 generates an AC voltage in response to the vibration of the cantilever portion 122 of the cantilever beam forming substrate 120. The cantilever beam forming substrate 120 has a weight portion 123 and is disposed inside the frame-shaped support portion 121 and the support portion 121. The weight portion 123 is supported by the support portion 121 via the cantilever portion 122 so as to be swingable. The piezoelectric conversion portion 124 is formed on the cantilever portion 122 on one surface side of the cantilever forming substrate 120.

The support portion 121, the cantilever portion 122, and the weight portion 123 are formed using the element forming substrate 120a. In Document 1, an SOI (Silicon On Insulator) substrate or the like is used as the element forming substrate 120a.

The piezoelectric conversion portion 124 is configured by a lower electrode 124a, a piezoelectric layer 124b, and an upper electrode 124c.

In the prior art, a thermal flow sensor using a heater is known as a flow sensor having a bridge circuit (for example, refer to Japanese Patent Laid-Open Publication No. 2002-310762). Japanese Patent Publication No. 2002-310762 is referred to as Document 2.

Document 2 describes a thermal flow sensor in which a resistor for a bridge circuit is integrated with a heater, a resistance thermometer, and a temperature sensor on the same semiconductor substrate.

In addition, it has been proposed to use a power generating mechanism that vibrates a piezoelectric element by wind power as a sensor for detecting wind speed (for example, refer to Japanese Patent Laid-Open Publication No. 2010-106809). Japanese Patent Publication No. 2010-106809 is referred to as Document 3.

This power generating mechanism includes, for example, a piezoelectric element 110, a holding body 140, a wind receiving blade 120, and a connecting body 130, as shown in FIG. The holding body 140 is fixed to the piezoelectric element 110. The connector 130 connects the wind receiving wing 120 to the piezoelectric element 110. The connecting body 130 transmits the vibration motion or the like of the airfoil 120 to the piezoelectric element 110. Further, the power generation mechanism has eight piezoelectric elements 110, a wind receiving blade 120, and a connecting body 130 in each of the holding bodies 140.

The piezoelectric element 110 is a piezoelectric double layer actuating element. The piezoelectric double-layer actuating element utilizes two PZT-based ceramic plates to sandwich a stainless steel shim.

Document 3 shows an example of the relationship between the average wind speed and the generated voltage, and it is described that "the average wind speed reaches an increase in the generated voltage of about 7 m/sec, and the generated voltage decreases after the passage".

Further, Document 3 discloses a piezoelectric power generation module including, for example, a power generation mechanism that vibrates a piezoelectric element by a wind force, a power storage mechanism that stores electric energy generated by the power generation mechanism, and an electric circuit that is an intermittent self-storage mechanism. Supply electricity. Further, Document 3 describes a wireless transmission system. The wireless transmission system is configured to include a wireless transmission module that supplies electric power from the piezoelectric power generation module described above and intermittently transmits data of wind speed. Further, Document 3 describes a wind speed monitoring system including the wireless transmission module and a receiver for transmitting signals.

In addition, the thermal flow sensor must pass current through the heater, which is difficult to reduce power consumption.

Further, the power generation mechanism estimates that the piezoelectric element 110 can be continuously vibrated by generating a Karman vortex. However, in the above-described power generating mechanism, the holding body 140, the connecting body 130, and the wind receiving blade 120 are required in addition to the piezoelectric element 110, and the power generating mechanism is increased in size with respect to the piezoelectric element 110. Therefore, when the above-described power generating mechanism is used as the sensor for detecting the wind speed, it is difficult to miniaturize the sensor for detecting the wind speed.

The inventor of the present invention designed to generate electricity by vibrating the cantilever portion 122 of the power generating device by a fluid. Therefore, the inventors of the present invention have investigated that the power generating device is disposed in a flow path of a fluid, and the power generating device generates power by using a fluid instead of external vibration.

However, it is difficult for the above-described power generation device to generate electricity by using a fluid.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a piezoelectric conversion device and a flow rate sensor using the same that can perform fluid-induced vibration and achieve piezoelectric conversion efficiency when fluid-induced vibration is increased.

A piezoelectric transducer according to the present invention includes: a support portion; an opposite portion facing the support portion; and a vibration block located between the support portion and the opposite portion. One end of the vibration block is fixed to the support portion, and the other end is spaced apart from the opposite portion. The vibration block includes: a beam portion; a weight portion; a protrusion portion; and a piezoelectric conversion portion. The beam portion is thinner than the support portion and is supported by the support portion in a freely swinging manner. The weight portion is provided at a front end of the beam portion and is thicker than the beam portion. The protruding portion protrudes toward the opposite side of the beam portion side from the weight portion, and is thinner than the weight portion and the opposing portion. The piezoelectric conversion unit generates an AC voltage in response to the vibration of the beam portion. The vibration block is warped so that the normal line of the front end face of the protrusion does not intersect the opposite portion. Thereby, in the piezoelectric conversion device of the present invention, it is possible to perform fluid-induced vibration and achieve piezoelectric conversion efficiency when lifting fluid-induced vibration. effect.

In the piezoelectric conversion device, it is preferable that the natural frequency of the protruding portion is greater than the natural frequency of the vibration block.

In the piezoelectric transducer device, it is preferable that the opposing portion has an inclined surface between the opposing surface facing the supporting portion and a surface in the thickness direction of the opposing portion, the inclined surface making the protruding portion The distance between the opposing portions is lengthened.

In the piezoelectric transducer, it is preferable that the opposing portion has a second protruding portion that protrudes toward the first protruding portion side of the protruding portion, and the second protruding portion is warped toward the opposite side of the first protruding portion.

In the piezoelectric transducer device, it is preferable that the vibration block is formed with a concave portion on a surface farther from the beam portion among the two faces in the thickness direction of the weight portion.

In the piezoelectric conversion device, it is preferable that the beam portion is composed of a first ruthenium layer and a first insulating film formed on one surface side in the thickness direction of the first ruthenium layer. The first insulating film is warped by the compressive stress of the first insulating film. The protruding portion is formed by a second layer and a second insulating film formed on one surface side in the thickness direction of the second layer. The second insulating film is warped by the compressive stress of the second insulating film.

In the piezoelectric conversion device, it is preferable that the beam portion is composed of a first ruthenium layer and a first insulating film formed on one surface side in the thickness direction of the first ruthenium layer. The first insulating film is warped by the compressive stress of the first insulating film. The first protruding portion is configured by a second ruthenium layer and a second insulating film formed on one surface side in the thickness direction of the second ruthenium layer. The second insulating film is warped by the compressive stress of the second insulating film. The second protruding portion is composed of a third insulating layer and a third insulating film formed on one surface side in the thickness direction of the third insulating layer. The third insulating film is warped by the tensile stress of the third insulating film.

In the piezoelectric conversion device, it is preferable to make the top view shape of the vibration block in the vibration block shape. The width of the beam portion in the vibration block is the same as the width of the weight portion. The value obtained by dividing the length of the weight portion by the sum of the length of the weight portion and the length of the beam portion is 0.4 or more and 0.6 or less.

The flow sensor of the present invention is characterized by comprising the piezoelectric conversion device; and a detecting portion for detecting an alternating voltage generated by the piezoelectric conversion portion. Therefore, in the flow rate sensor of the present invention, since the piezoelectric transducer can be used to perform fluid-induced vibration and increase the piezoelectric conversion efficiency when the fluid induces vibration, it is possible to achieve low power consumption and miniaturization. effect.

The flow sensor preferably includes a wireless transmission unit that intermittently transmits a wireless signal including the detection result of the detection unit.

The flow sensor preferably includes: a power storage unit; and a switching circuit. The power storage unit rectifies and stores the AC voltage generated by the piezoelectric conversion unit. The switching circuit is configured to be switchable between a first state and a second state. In the first state, the piezoelectric conversion unit is electrically connected to the power storage unit. In the second state, the piezoelectric conversion unit is electrically connected to the detection unit. The detecting unit and the wireless transmitting unit can operate the power storage unit as a power source.

1‧‧‧Piezoelectric conversion device

2‧‧‧Detection Department

5‧‧‧Power Storage Department

6‧‧‧Wireless Transmission Department

7‧‧‧ Electricity storage monitoring department

9‧‧‧Switching circuit

10‧‧‧Substrate

10a‧‧‧矽 substrate

10b‧‧‧ buried oxide film

10c‧‧‧ layer

10ca‧‧‧1st floor

10cc‧‧‧2nd layer

10cd‧‧‧3rd layer

10d‧‧‧slit

10e‧‧‧ sloped surface

10f‧‧‧ space

10h‧‧‧1st trench

10i‧‧‧2nd trench

11‧‧‧Framework

11a‧‧‧Support Department

11b‧‧‧ opposite department

11c‧‧‧Link Department

12‧‧‧Vibration block

12a‧‧ ‧ Beam Department

12b‧‧‧weight department

12bb‧‧‧ recess

12c‧‧‧ highlights

12cc‧‧‧ front end

13‧‧‧2nd protrusion

14‧‧‧Piezoelectric conversion department

14a‧‧‧1st electrode (lower electrode)

14b‧‧‧piezoelectric layer

14c‧‧‧2nd electrode (upper electrode)

15‧‧‧ flow path

16a‧‧‧1st wiring

16c‧‧‧2nd wiring

17a‧‧‧1st pad electrode

17c‧‧‧2nd pad electrode

18a, 18b, 18c‧‧ ‧ insulating film

18aa‧‧‧1st insulating film

18ac‧‧‧2nd insulation film

18cc‧‧‧3rd insulating film

19‧‧‧Insulation

71‧‧‧Wireless Receiving Department

72‧‧‧Control Department

73‧‧‧Electric motor

74‧‧‧fan

75‧‧‧Operation switch

76‧‧‧Setting Department

110‧‧‧Piezoelectric components

120‧‧‧Wind wing

120a‧‧‧Component forming substrate

121‧‧‧Support Department

122‧‧‧Cantilever beam

123‧‧‧With the weight department

124‧‧‧Piezoelectric conversion department

124a‧‧‧lower electrode

124b‧‧‧Piezoelectric layer

124c‧‧‧ upper electrode

130‧‧‧Connector

140‧‧‧ Keeping body

141‧‧‧1st piezoelectric transducer

142‧‧‧2nd piezoelectric transducer

A1‧‧‧Flow Sensor

A2‧‧‧Air conditioner

F1‧‧‧Related cases

F2‧‧‧Related cases

F3‧‧‧Related cases

La‧‧‧ Length

Lb‧‧‧ length

Ha‧‧‧Width

Hb‧‧‧Width

Preferred embodiments of the present invention are described in more detail below. Other features and advantages of the present invention will be further understood from the following detailed description and appended claims.

Fig. 1A is a schematic plan view of a piezoelectric transducer according to a first embodiment. Fig. 1B is a schematic cross-sectional view taken along line X-X of Fig. 1A.

2A to 2F are cross-sectional views showing main steps of a method of manufacturing the piezoelectric transducer according to the first embodiment.

Fig. 3 is a view showing the size of a piezoelectric transducer according to a first embodiment;

Fig. 4 is a view showing the relationship between the resonance frequency of the vibration block and the critical flow velocity generated by the fluid induced vibration in the piezoelectric conversion device according to the first embodiment.

Fig. 5 is a graph showing the vibration characteristics of the piezoelectric transducer of the first embodiment.

Fig. 6 is a graph showing the vibration characteristics of the piezoelectric transducer of the first embodiment.

Fig. 7 is a graph showing the vibration characteristics of the piezoelectric transducer of the first embodiment.

Fig. 8 is a simulation result showing the relationship between the ratio of the weight portion and the amount of change in the resonance frequency in the piezoelectric transducer of the first embodiment.

Fig. 9A is a schematic plan view showing a first modification of the piezoelectric transducer of the first embodiment. Fig. 9B is a schematic cross-sectional view taken along line X-X of Fig. 9A.

Fig. 10A is a schematic plan view showing a second modification of the piezoelectric transducer of the first embodiment. Fig. 10B is a schematic cross-sectional view taken along line X-X of Fig. 10A.

Fig. 11 is a view showing the size of a second modification of the piezoelectric transducer of the first embodiment.

Fig. 12 is a vibration characteristic diagram of a second modification of the piezoelectric transducer of the first embodiment.

Fig. 13A is a schematic plan view of a piezoelectric transducer according to a second embodiment. Figure 13B is a schematic cross-sectional view taken along line X-X of Figure 13A.

Fig. 14 is a schematic configuration diagram of a flow rate sensor of the third embodiment.

Fig. 15 is a view showing the characteristics of the flow rate sensor of the third embodiment.

Fig. 16 is a characteristic explanatory view of the flow rate sensor of the third embodiment.

Fig. 17 is a schematic block diagram showing a first modification of the flow rate sensor of the third embodiment.

Fig. 18 is a schematic configuration diagram of an air conditioning management system in the third embodiment.

Fig. 19 is a schematic block diagram showing a second modification of the flow rate sensor of the third embodiment.

Fig. 20A is a schematic plan view of a conventional power generating device. Fig. 20B is a schematic cross-sectional view taken along line A-A' of Fig. 20A.

Fig. 21 is an explanatory view schematically showing a power generating mechanism in another conventional example.

[Best Mode for Carrying Out the Invention]

(Embodiment 1)

The piezoelectric transducer 1 of the present embodiment will be described below with reference to Fig. 1 .

The piezoelectric conversion device 1 includes a support portion 11a, and the opposite portion 11b is opposed to the support portion 11a. And the vibration block 12 is located between the support portion 11a and the opposite portion 11b. The vibration block 12 is fixed at one end to the support portion 11a, and the other end is spaced apart from the opposite portion 11b. Thereby, the piezoelectric conversion device 1 forms a flow path 15 through which the fluid can pass between the other end of the vibration block 12 and the opposite portion 11b. The piezoelectric transducer 1 is configured such that the relative positional relationship between the support portion 11a and the opposing portion 11b is constant.

The vibration block 12 includes a beam portion 12a that is supported by the support portion 11a so as to be freely swayable, a weight portion 12b that is provided at the front end of the beam portion 12a, and a protruding portion 12c that protrudes toward the side opposite to the beam portion 12a side of the weight portion 12b. And a piezoelectric conversion portion 14. Therefore, the protruding portion 12c protrudes from the weight portion 12b. In the vibration block 12, one end (fixed end) of the vibration block 12 is constituted by the end of the beam portion 12a on the side of the support portion 11a, and the other end of the vibration block 12 is constituted by the front end in the projecting portion 12c (free end) ).

The beam portion 12a is thinner than the support portion 11a. The weight portion 12b is thicker than the beam portion 12a. Further, the protruding portion 12c is thinner than the weight portion 12b and the opposing portion 11b. The piezoelectric transducer 14 generates an AC voltage in response to the vibration of the beam portion 12a of the vibration block 12. The vibration block 12 is warped so that the normal line of the front end surface 12cc of the protruding portion 12c does not intersect the opposite portion 11b. Thereby, the piezoelectric transducer 1 can perform fluid-induced vibration and achieve piezoelectric conversion efficiency when the fluid-induced vibration is increased. The fluid-induced vibration system is in a state in which the piezoelectric transducer 1 is placed in the flow field, and the vibration of the vibration block 12 generated by the fluid flowing in the flow field through the flow path 15 is generated. This fluid induces vibration to self-induced vibration. As the fluid, there are, for example, air, a gas, a mixed gas of air and gas, a liquid, and the like. When the fluid is a gas, the flow field is not particularly limited, for example, inside the air supply duct of the air conditioner or inside the exhaust duct of the air conditioner. The piezoelectric conversion device 1 can increase the inertial force of the vibration of the vibration block 12 by increasing the vibration force of the vibration block 12 by the vibration portion 12 having the weight portion 12b as compared with the case where the weight portion 12b is not provided. The amplitude of block 12. Further, the piezoelectric transducer 1 has the weight portion 12b by the vibration block 12, and when the vibration block 12 vibrates, the strain is generated in the beam portion 12a and the piezoelectric transducer portion 14 in a concentrated manner, and the lifting can be achieved. Piezoelectric conversion efficiency. Further, the piezoelectric transducer 1 has the weight portion 12b by the vibration block 12, so that the resonance frequency of the vibration block 12 can be reduced, and the flow velocity of the fluid that causes the vibration block 12 to start to vibrate can be reduced. Further, the piezoelectric transducer 1 has the opposing portion 11b, and the vibration of the vibration block 12 is easily caused by the flow of the fluid flowing through the flow path 15.

The piezoelectric conversion device 1 is preferably such that the natural frequency of the protruding portion 12c is larger than the natural frequency of the vibration block 12. Thereby, the piezoelectric transducer 1 can suppress the protrusion 12c from being oscillated by the weight portion 12b as a base point, and can suppress the vibration energy reduction caused by the vibration of the protrusion 12c alone.

Each component of the piezoelectric transducer 1 will be described in detail below.

The piezoelectric conversion device 1 can be manufactured using a manufacturing technique of MEMS (micro electro mechanical systems).

In the piezoelectric transducer 1 , the support portion 11 a , the opposing portion 11 b , the beam portion 12 a , the weight portion 12 b , and the protruding portion 12 c are formed by the substrate 10 . The piezoelectric conversion device 1 is formed with a beam portion 12a and a protruding portion 12c on one surface side of the substrate 10. The substrate 10 has a surface and another surface. Hereinafter, one surface of the substrate 10 is also referred to as a first surface, and the other surface of the substrate 10 is also referred to as a second surface.

The piezoelectric conversion device 1 preferably includes a frame-shaped frame portion 11 having a support portion 11a and an opposite portion 11b. That is, the piezoelectric transducer 1 preferably forms the frame portion 11, the beam portion 12a, the weight portion 12b, and the protruding portion 12c from the substrate 10. In other words, the support portion 11a and the opposing portion 11b are preferably configured by a part of the frame portion 11. Thereby, the piezoelectric transducer 1 can improve the relative positional accuracy of the support portion 11a and the opposing portion 11b. Further, the piezoelectric transducer 1 can improve the relative positional accuracy of the vibration block 12 and the opposing portion 11b. In the following, the two portions of the frame portion 11 that connect the support portion 11a and the opposing portion 11b are referred to as a connecting portion 11c.

As the substrate 10, for example, an SOI substrate formed of a buried oxide film 10b formed on the germanium substrate 10a and a germanium layer 10c embedded in the oxide film 10b can be used. Further, the buried oxide film 10b is composed of a hafnium oxide film. The first surface of the substrate 10 is defined as a (100) plane, but is not limited to the (100) plane, and may be, for example, a (110) plane.

The support portion 11a, the opposing portion 11b, and the respective connecting portions 11c may be formed by the tantalum substrate 10a and the buried oxide film 10b and the tantalum layer 10c among the SOI substrates.

The beam portion 12a is formed by the tantalum layer 10c among the SOI substrates. The beam portion 12a has a thickness smaller than that of the support portion 11a and has flexibility.

The protruding portion 12c is formed of the ruthenium layer 10c among the SOI substrates, and has a thickness smaller than that of the support portion 11a and the opposite portion 11b. The piezoelectric conversion device 1 sets the length of the protruding portion 12c to be shorter than the length of the beam portion 12a such that the natural frequency of the protruding portion 12c is larger than the natural frequency of the vibration block 12.

The piezoelectric transducer 1 electrically insulates the substrate 10 from the piezoelectric conversion portion 14 by the insulating film 18a formed on the first surface side of the substrate 10. The insulating film 18a can be formed, for example, by a ruthenium oxide film. The ruthenium oxide film is formed by, for example, a thermal oxidation method, but is not limited thereto, and may be formed by a CVD (Chemical Vapor Deposition) method or the like.

The piezoelectric transducer 1 is configured to constitute a beam portion 12a: a part of the ruthenium layer 10c, and a part of the insulating film 18a formed on one surface side in the thickness direction of the ruthenium layer 10c. Here, the insulating film 18a has a compressive stress. Therefore, the beam portion 12a is configured by the first layer 10ca of the portion of the layer 10c that constitutes the beam portion 12a, and the one surface of the insulating layer 18a that is formed in the thickness direction of the first layer 10ca. The first insulating film 18aa at the portion is warped by the compressive stress of the first insulating film 18aa.

Further, the piezoelectric transducer 1 is configured to constitute a protruding portion 12c: a part of the ruthenium layer 10c; and a part of the insulating film 18a formed on one surface side in the thickness direction of the ruthenium layer 10c. Here, the insulating film 18a has a compressive stress. Therefore, the protruding portion 12c is configured by the second 矽 layer 10cc at the portion of the 矽 layer 10c constituting the protruding portion 12c, and the one surface side of the insulating film 18a formed in the thickness direction of the second 矽 layer 10cc. The second insulating film 18ac at the portion is warped by the compressive stress of the second insulating film 18ac.

In the piezoelectric conversion device 1, the insulating film 18a formed on the first surface side of the substrate 10 not only has a function of electrically insulating the substrate 10 from the piezoelectric conversion portion 14, but also has the beam portion 12a and the protruding portion 12c warped. Features. Thereby, the piezoelectric conversion device 1 can make the manufacturing process as compared with the case where the film for stress control is formed on the beam portion 12a and the protruding portion 12c separately from the insulating film 18a. simplify.

The substrate 10 is not limited to the SOI substrate, and a single crystal germanium substrate, a polycrystalline germanium substrate, a magnesium oxide (MgO) substrate, a metal substrate, a glass substrate, a polymer substrate, or the like can be used.

The frame portion 11 preferably has a frame shape and a rectangular frame shape. That is, the frame portion 11 should preferably have a rectangular outer shape. In addition, a rectangle means not only a rectangle but also a square. Thereby, the piezoelectric conversion device 1 can enhance the workability of the wafer cutting step at the time of manufacture. At the time of manufacture of the piezoelectric transducer 1, for example, an SOI wafer is first prepared as a wafer to be the basis of the frame portion 11, the beam portion 12a, the weight portion 12b, and the protruding portion 12c. In the manufacture of the piezoelectric conversion device 1, the previous steps of forming a plurality of piezoelectric conversion devices 1 on a wafer are performed, and in the subsequent steps, the respective piezoelectric conversion devices 1 are separated by a wafer cutting step. Further, the manufacturing method of the piezoelectric conversion device 1 will be described later.

The inner peripheral shape of the frame portion 11 is not limited to a rectangular shape, and may be a shape such as a polygon other than a rectangle, a circle, or an ellipse. Further, the outer peripheral shape of the frame portion 11 may be a shape other than a rectangle.

The piezoelectric transducer 1 arranges the vibration block 12 inside the frame portion 11 in plan view. The piezoelectric conversion device 1 is formed with a U-shaped slit 10d that surrounds the vibration block 12 in a plan view on the substrate 10. The U-shaped slit 10d spatially separates the portion other than the joint portion of the vibration block 12 with the frame portion 11 from the frame portion 11. Thereby, the planar shape of the vibration block 12 is formed in a rectangular shape. In the piezoelectric conversion device 1, the slit 10d constitutes the flow path 15.

The piezoelectric conversion portion 14 is formed on the insulating film 18a. The piezoelectric transducer 14 has a first electrode (lower electrode) 14a, a piezoelectric layer 14b, and a second electrode (upper electrode) 14c in this order from the side of the beam portion 12a. In other words, the piezoelectric transducer portion 14 includes the piezoelectric layer 14b, and the first electrode 14a and the second electrode 14c, which are opposed to each other with the piezoelectric layer 14b interposed therebetween from both sides in the thickness direction.

In the piezoelectric transducer device 1, the piezoelectric layer 14b of the piezoelectric transducer portion 14 is subjected to stress by the vibration of the vibration block 12, and a charge imbalance occurs in the second electrode 14c and the first electrode 14a, and in the piezoelectric transducer portion 14 Generate an AC voltage. Therefore, the piezoelectric conversion device 1 is a piezoelectric conversion portion 14 The piezoelectric effect of the piezoelectric material is used to generate an alternating voltage. The piezoelectric conversion device 1 can be used as a vibration type power generation device.

The planar shape of the piezoelectric body layer 14b may be formed in a rectangular shape. The planar size of the piezoelectric layer 14b is set to be slightly smaller than the planar size of the first electrode 14a and slightly larger than the planar size of the second electrode 14c. Hereinafter, in the thickness direction of the vibration block 12, the region where the first electrode 14a, the piezoelectric layer 14b, and the second electrode 14c overlap is referred to as a piezoelectric conversion region.

The piezoelectric transducer 1 connects the support portion 11a and the vibration block 12 in a plan view, and aligns the end of the piezoelectric conversion region on the support portion 11a side with the boundary between the support portion 11a and the vibration block 12, that is, the first boundary. Thereby, the piezoelectric transducer 1 can vibrate the vibration block 12 as compared with the case where the end of the piezoelectric conversion region on the support portion 11a side is located closer to the vibration block 12 than the first boundary. The area of the piezoelectric conversion region where the enlarged portion is increased increases the piezoelectric conversion efficiency.

Further, the piezoelectric transducer 1 connects the support portion 11a and the vibration block 12 in a plan view, and the end of the piezoelectric conversion region on the side of the weight portion 12b is aligned with the boundary between the beam portion 12a and the weight portion 12b. The second boundary. Thereby, the piezoelectric transducer 1 can vibrate the vibration block 12 as compared with the case where the end on the weight portion 12b side of the piezoelectric conversion region is located closer to the beam portion 12a than the second boundary. The area of the piezoelectric conversion region where the enlarged portion is increased increases the piezoelectric conversion efficiency.

The AC voltage generated by the piezoelectric transducer 14 is an AC voltage in response to the sinusoidal waveform of the vibration of the piezoelectric layer 14b. The piezoelectric conversion portion 14 of the piezoelectric conversion device 1 can generate electric power by self-induced vibration generated by the flow of the fluid in the flow path 15. The resonance frequency of the piezoelectric conversion device 1 is determined by the structural parameters, materials, and the like of the vibration block 12.

In the piezoelectric transducer device 1, the first pad electrode 17a is provided in the support portion 11a, and is electrically connected to the first electrode 14a via the first wiring 16a. In the piezoelectric transducer device 1, the second pad electrode 17c is provided in the support portion 11a, and is electrically connected to the second electrode 14c via the second wiring 16c. First wiring 16a, The material of the second wiring 16c, the first pad electrode 17a, and the second pad electrode 17c is Au. However, it is not limited to Au, and may be, for example, Mo, Al, Pt, or Ir. Further, the materials of the first wiring 16a, the second wiring 16c, the first pad electrode 17a, and the second pad electrode 17c are not limited to the same material, and different materials may be used individually.

Further, the first wiring 16a, the second wiring 16c, the first pad electrode 17a, and the second pad electrode 17c are formed of a metal layer having a single layer structure. However, the first wiring 16a, the second wiring 16c, the first pad electrode 17a, and the second pad electrode 17c are not limited to being formed of a metal layer having a single layer structure, and may be configured by a multilayer structure of two or more layers.

Further, the piezoelectric conversion device 1 is provided with an insulating layer 19 to prevent short-circuiting between the second wiring 16c and the first electrode 14a. The insulating layer 19 is composed of a hafnium oxide film. However, the insulating layer 19 is not limited to the hafnium oxide film, and may be formed, for example, of a tantalum nitride film.

The piezoelectric material of the piezoelectric layer 14b is PZT (Pb(Zr, Ti)O ₃ ). However, the piezoelectric material is not limited to PZT (Pb(Zr, Ti)O ₃ ), and may be, for example, PZT-PMN (Pb(Mn, Nb)O ₃ ) or PZT to which other impurities are added. Moreover, the piezoelectric material may be AlN, ZnO, KNN (K _0.5 Na _0.5 NbO ₃ ) or added impurities (such as Li, Nb, Ta, Sb, Cu, etc.) to KN (KNbO ₃ ), NN (NaNbO ₃ ), and KNN. ) and so on. The piezoelectric transducer device 1 preferably has a piezoelectric layer 14b formed of a piezoelectric film.

The material of the first electrode 14a is Pt, but is not limited to Pt, and may be, for example, Au, Al, Ir or the like. Further, the material of the second electrode 14c is Au, but is not limited to Au, and may be, for example, Mo, Al, Pt, Ir or the like.

The piezoelectric transducer 1 sets the thickness of the first electrode 14a to 500 nm, the thickness of the piezoelectric layer 14b to 3000 nm, and the thickness of the second electrode 14c to 500 nm. However, these numerical values are merely examples and are not particularly limited.

The piezoelectric conversion device 1 may be a structure in which a buffer layer is provided between the substrate 10 and the first electrode 14a. The buffer layer serves to enhance the crystallinity of the piezoelectric layer 14b on the first electrode 14a. The material of the buffer layer may be appropriately selected in accordance with the piezoelectric material of the piezoelectric layer 14b. In the case where the piezoelectric material of the piezoelectric layer 14b is PZT, for example, SrRuO ₃ , (Pb, La)TiO ₃ , PbTiO ₃ , MgO, LaNiO ₃ or the like is preferably used. Further, the buffer layer may be formed of, for example, a laminated film of a Pt film and a SrRuO ₃ film. Further, the piezoelectric conversion device 1 can improve the crystallinity of the piezoelectric layer 14b by providing a buffer layer.

The configuration of the piezoelectric transducer 1 is not limited to the above-described example. For example, the width of the beam portion 12a in the piezoelectric transducer portion 14 in the width direction (the vertical direction of FIG. 1A) may be reduced in size and applied to one beam. On one surface side of the portion 12a, a plurality of piezoelectric conversion portions 14 are arranged side by side in the width direction. In this case, the piezoelectric conversion device 1 can be configured to electrically connect one end of the series circuit of the plurality of piezoelectric conversion portions 14 to the first pad electrode 17a, and electrically connect the other end of the series circuit to the second pad electrode. 17c.

A method of manufacturing the piezoelectric conversion device 1 will be described below.

At the time of manufacture of the piezoelectric transducer 1, first, the substrate 10 composed of the SOI substrate is prepared (see FIG. 2A), and then the first step is performed. In the first step, an insulating film 18a made of a hafnium oxide film is formed on the first surface side of the substrate 10 by thermal oxidation or the like, and is formed on the other surface of the substrate 10, that is, on the second surface side. An insulating film 18b made of a ruthenium film (see FIG. 2B). In the first step, a thermal oxidation method is employed as the method of forming the insulating film 18a and the insulating film 18b. However, it is not limited to the thermal oxidation method, and a CVD method or the like may be employed.

In the method of manufacturing the piezoelectric transducer 1, the second step and the third step are sequentially performed after the first step. In the second step, the first conductive layer is formed on the entire surface side of the first surface of the substrate 10 as the basis of the first electrode 14a and the first wiring 16a. In the second step, the sputtering method is used for the method of forming the first conductive layer. However, the sputtering method is not limited thereto, and for example, a CVD method or a vapor deposition method may be employed. In the third step, a piezoelectric material layer which is the basis of the piezoelectric layer 14b is formed. The method of forming the piezoelectric material layer in the third step is a sputtering method, but is not limited to the sputtering method. For example, a CVD method or a sol-gel method may be employed.

In the method of manufacturing the piezoelectric transducer 1, the fourth step and the fifth step are sequentially performed after the third step. In the fourth step, the piezoelectric material layer is patterned into a predetermined shape of the piezoelectric body layer 14b by a lithography technique and an etching technique. In the fifth step, the first conductive layer is patterned into a predetermined shape of the first electrode 14a and the first wiring 16a by a lithography technique and an etching technique.

In the method of manufacturing the piezoelectric transducer 1, the sixth step, the seventh step, and the eighth step are sequentially performed after the fifth step. In the sixth step, the insulating layer 19 is formed on the first surface side of the substrate 10. In the sixth step, the insulating layer 19 is formed by lift-off. The method of forming the insulating layer 19 in the sixth step is not limited to the detachment method. In the seventh step, the second conductive layer is formed on the entire surface side of the first surface of the substrate 10 as the basis of the second electrode 14c and the second wiring 16c. Although the method of forming the second conductive layer in the seventh step is a sputtering method, it is not limited to the sputtering method, and for example, a CVD method or a vapor deposition method may be employed. In the eighth step, the second conductive layer is patterned into a predetermined shape of the second electrode 14c and the second wiring 16c by a lithography technique and an etching technique (see FIG. 2C).

In the method of manufacturing the piezoelectric transducer 1, the ninth step and the tenth step are sequentially performed after the eighth step. In the ninth step, the third conductive layer is formed on the entire surface side of the first surface of the substrate 10 as the basis of the first pad electrode 17a and the second pad electrode 17c. Although the method of forming the third conductive layer in the ninth step is a sputtering method, it is not limited to the sputtering method, and for example, a CVD method or a vapor deposition method may be employed. In the tenth step, the third conductive layer is patterned into a predetermined shape of the first pad electrode 17a and the second pad electrode 17c by a lithography technique and an etching technique. In the method of manufacturing the piezoelectric transducer 1, the first pad electrode 17a and the second pad electrode 17c may be formed by a lift-off method instead of the ninth step and the tenth step which are sequentially performed. Further, in the method of manufacturing the piezoelectric transducer 1, the first pad electrode 17a and the second pad electrode 17c may be formed by a vapor deposition method or the like by using a metal mask or the like instead of sequentially. Step 9 and step 10.

In the method of manufacturing the piezoelectric transducer 1, the eleventh step and the twelfth step are sequentially performed after the tenth step. In the eleventh step, the predetermined formation region of the slit 10d is etched from the first surface side of the substrate 10 to the first predetermined depth, thereby forming the first trench 10h (see FIG. 2D). The predetermined formation region of the slit 10d can be set to correspond to the support portion 11a, the opposing portion 11b, the respective coupling portions 11c, the beam portion 12a, the weight portion 12b, and the projection in the substrate 10 that has been completed in the tenth step. A portion other than the portion of the portion 12c. In the eleventh step, the insulating film 18a and the germanium layer 10c are etched by a lithography technique, an etching technique, or the like to form the first trench 10h. The etching in the eleventh step is preferably dry etching using an inductively coupled plasma type dry etching apparatus which can vertically dig deep. In the eleventh step, the buried oxide film 10b of the substrate 10 can be used as an etching stopper. In the twelfth step, the portions corresponding to the support portion 11a, the opposing portion 11b, the respective connecting portions 11c, and the weight portion 12b are removed from the second surface side of the substrate 10, and are etched up to the second predetermined depth to form the first 2 groove 10i (refer to Fig. 2E). In the twelfth step, the insulating film 18b and the germanium substrate 10a are etched by a lithography technique, an etching technique, or the like to form the second trench 10i. The etching in the twelfth step is preferably dry etching using an inductively coupled plasma type dry etching apparatus which can vertically dig deep. In the twelfth step, the buried oxide film 10b of the substrate 10 can be used as an etching stopper. The manufacturing method of the piezoelectric conversion device 1 can also reverse the order of the eleventh step and the twelfth step.

In the method of manufacturing the piezoelectric conversion device 1, the thirteenth step is performed after the eleventh step and the twelfth step. In the thirteenth step, the oxide film 10b is buried in the predetermined formation region of the slit 10d, the predetermined formation region of the beam portion 12a, and the portion of the predetermined formation region of the projection portion 12c, and are etched. In the manufacturing method of the piezoelectric transducer 1, the slit 10d, the beam portion 12a, and the protruding portion 12c are formed by performing the thirteenth step (see FIG. 2F). Further, in the thirteenth step, the buried oxide film 10b and the insulating film 18b are etched. In the manufacturing method of the piezoelectric transducer 1, the piezoelectric transducer 1 is obtained by performing the steps from the first step to the thirteenth step.

In the manufacture of the piezoelectric transducer 1, the wafer level can be completed until the end of the thirteenth step, and then divided into the respective piezoelectric transducers 1 by performing a wafer dicing step.

In the manufacturing method of the piezoelectric conversion device 1, when the vibration block 12 is formed by etching the buried oxide film 10b in the thirteenth step, the vibration block 12 can be warped. The piezoelectric conversion device 1 warps the vibration block 12 by the internal stress of the insulating film 18a, that is, the compressive stress. In the method of manufacturing the piezoelectric conversion device 1, the internal stress of the insulating film 18a can be controlled by appropriately setting the process conditions of the insulating film 18a when the insulating film 18a is formed. The internal stress of the insulating film 18a can be controlled by, for example, setting the insulating film 18a by thermal oxidation. Further, the internal stress of the insulating film 18a is insulated, for example, by sputtering or CVD. The film formation of the film 18a can be controlled by appropriately setting process conditions such as gas pressure or temperature.

In the initial state in which the vibration block 12 does not have external vibration or fluid or the like, the piezoelectric block 1 is warped so that the normal line of the end surface 12cc before the projection 12c does not intersect the opposite portion 11b. Since the vibrating block 12 is warped by the protruding portion 12c, it is possible to cross the surface of the front end surface 12cc along the protruding portion 12c and the surface of the opposing portion 11b that faces the support portion 11a. Here, the one side of the vibration block 12 in the thickness direction is a concave curved surface, and the other surface side is a convex curved surface.

The piezoelectric transducer 1 is disposed such that when the vibration block 12 is to be subjected to fluid-induced vibration, the first surface side of the substrate 10 is the upstream side of the fluid, and the second surface side of the substrate 10 is the downstream side of the fluid. . In other words, the piezoelectric conversion device 1 is disposed such that one side (top surface of FIG. 1B) in the thickness direction of the opposing portion 11b is the upstream side of the fluid and the other side in the thickness direction of the opposing portion 11b (FIG. 1B) The bottom side is the downstream side of the fluid. In the piezoelectric conversion device 1, the flow velocity when the fluid flowing from the upstream side toward the piezoelectric conversion device 1 passes through the flow passage 15 becomes faster. In the piezoelectric transducer device 1, after the flow velocity of the fluid is increased, the pressure of the weight portion 12b, the protruding portion 12c, and the space 10f surrounded by the opposing portion 11b is lowered, so that the protruding portion 12c is displaced toward the opposing portion 11b. In other words, in the piezoelectric conversion device 1, the protruding portion 12c is displaced toward the space 10f side. Further, in the piezoelectric transducer device 1, it is presumed that after the pressure difference between the both sides in the thickness direction of the protruding portion 12c disappears, the force of the vibration block 12 returning to the original position due to the elastic force of the vibration block 12 acts. . It is presumed that the piezoelectric transducer 1 repeats such an operation to cause the vibration block 12 to self-induced vibration, and an alternating voltage is generated in the piezoelectric transducer 14.

The piezoelectric transducer 1 of the present embodiment described above includes a support portion 11a, the opposite portion 11b is opposed to the support portion 11a, and the vibration block 12 is located between the support portion 11a and the opposite portion 11b. It is fixed to the support portion 11a, and the other end is spaced apart from the opposite portion 11b. The vibration block 12 includes a beam portion 12a, a weight portion 12b, a protruding portion 12c, and a piezoelectric conversion portion 14. The beam portion 12a is thinner than the support portion 11a, and the supported portion 11a is supported freely swinging. The weight portion 12b is provided at the front end of the beam portion 12a and thicker than the beam portion 12a. The protruding portion 12c protrudes toward the side opposite to the side of the beam portion 12a in the weight portion 12b, and is thinner than the weight portion 12b and the opposing portion 11b. The piezoelectric transducer 14 generates an AC voltage in response to the vibration of the beam portion 12a. The method in which the vibration block 12 is warped into the front end surface 12cc of the protruding portion 12c The line does not intersect the opposite portion 11b. Thereby, the piezoelectric conversion device 1 can perform fluid-induced vibration and achieve piezoelectric conversion efficiency when the fluid-induced vibration is increased.

Further, as a result of a special study by the inventors of the present invention, it has been found that sometimes the vibration is not induced in the low flow velocity region due to the structural parameters of the piezoelectric conversion device 1. Further, the inventors of the present invention have learned that sometimes due to the structural parameters of the piezoelectric transducer 1, the amplitude increases as the flow rate increases, and the piezoelectric conversion efficiency is saturated.

Therefore, as the structural parameters of the vibration block 12, as shown in Fig. 3, in the plan view of the state in which the vibration block 12 is not warped, it is assumed that the width of the beam portion 12a is Ha, and the width of the weight portion 12b is Hb, the beam The length of the portion 12a is La, and the length of the weight portion 12b is Lb. Further, the inventors of the present invention produced a plurality of piezoelectric transducers 1, which set the width Ha of the beam portion 12a to the width Hb of the weight portion 12b, and divide the length Lb of the weight portion 12b by the weight portion 12b. The value obtained by multiplying the length Lb by the sum of the lengths La of the beam portions 12a is different from the value obtained by multiplying by 100. Hereinafter, the value obtained by dividing the length Lb of the weight portion 12b by the sum of the length Lb of the weight portion 12b and the length La of the beam portion 12a by 100 is referred to as the ratio R of the weight portion 12b. Fig. 4 is a graph showing the relationship between the resonance frequency and the critical flow velocity at which the fluid-induced vibration is generated by measuring the resonance frequency and the critical flow velocity of the fluid-induced vibration for each piezoelectric transducer 1. The critical flow rate at which the fluid induced vibration occurs is the lower limit of the flow rate at which the self-induced vibration of the vibration block 12 can occur.

The inventor of the present invention knows from Fig. 4 that the critical flow velocity is approximately proportional to the resonance frequency, and in order to vibrate the vibration block 12 at a low flow velocity, the resonance frequency of the vibration block 12 must be lowered.

5 to 7 show the measurement results of the vibration characteristics of the piezoelectric transducer 1 of the ratio R of each weight portion 12b. In FIGS. 5 to 7, the horizontal axis represents the flow velocity of the fluid, and the vertical axis represents the amplitude of the vibration block 12. The ratio R of the weight portion 12b becomes 50% when La = Lb.

The piezoelectric transducer 1 having the vibration characteristics of FIG. 5 and the piezoelectric transducer 1 for obtaining the vibration characteristics of FIG. 6 have the same width Ha of the beam portion 12a and the width Hb of the weight portion 12b, and the weight portion The length Lb of 12b is different from the sum of the lengths La of the beam portions 12a. Get the vibration of Figure 6 The piezoelectric conversion device 1 is a system in which La+Lb is larger than the piezoelectric conversion device 1 that obtains the vibration characteristics of FIG. Further, the piezoelectric transducer 1 having the vibration characteristics of FIG. 7 is obtained, and the width Ha of the tie beam portion 12a and the width Hb of the weight portion 12b are shorter than those of the piezoelectric transducer 1 which obtains the vibration characteristics of FIG. Lb is larger than the piezoelectric conversion device 1 which obtains the vibration characteristics of Fig. 6.

In addition, in FIG. 5, the resonance frequency of the vibration block 12 of the piezoelectric transducer 1 of the ratio R=20%, 50% is 200 Hz and 170 Hz, respectively. Further, in Fig. 6, the resonance frequencies of the vibration blocks 12 of the piezoelectric transducer 1 of the ratio R = 80%, 50%, and 0% are 150 Hz, 200 Hz, and 300 Hz, respectively. Further, in Fig. 7, the resonance frequencies of the vibration blocks 12 of the piezoelectric transducer 1 of the ratio R = 35% and 65% are respectively 80 Hz and 80 Hz.

5 to 7, it is understood that the piezoelectric transformer 1 having a ratio R of 50% in the weight portion 12b has a tendency that the amplitude of the vibration block 12 becomes larger as the flow velocity increases, and the ratio R is In the piezoelectric conversion device 1 of 0%, 20%, 35%, 65%, and 80%, the amplitude of the vibration block 12 tends to be saturated as the flow rate increases. In this regard, the inventors of the present invention considered that the area of the beam portion 12a which is the elastic portion which generates the restoring force of the vibration block 12 can be obtained in the piezoelectric transducer 1 having the ratio R of 50%, and the fluid flow is withstand The balance of the area of the vibration block 12 caused by the pressure.

Fig. 8 shows a simulation result of the relationship between the ratio R of the weight portion 12b and the resonance frequency of the resonance frequency when the ratio R is 50%. The simulation system uses modal analysis (inherent value analysis) of the finite element method.

Fig. 8 is a simulation result when Ha = Hb; and La + Lb is a fixed value. As is clear from Fig. 8, the piezoelectric transducer 1 has a resonant frequency at the time when Ha = Hb and La + Lb is a fixed value and the ratio R of the weight portion 12b is 50%. Further, as described above, in order to vibrate the vibration block 12 at a lower flow rate, it is necessary to lower the resonance frequency of the vibration block 12. In other words, the piezoelectric conversion device 1 is defined as: Ha = Hb; La + Lb is a fixed value, and when the ratio R of the weight portion 12b is set to 50%, if La = Lb is determined, the fluid can be induced to vibrate. The critical flow rate is the slowest. Further, from Fig. 8, when the ratio R of the weight portion 12b is set to 40% or more and 60% or less, the resonance frequency is obtained. The amount of change in the rate is 2% or less, the difference in mass of the weight portion 12b is about 20%, and the difference in rigidity of the beam portion 12a is about 20%, and the ratio R to the weight portion 12b is expected to be 50%. Vibration characteristics.

From the above results, it is understood that the piezoelectric transducer device 1 preferably has a rectangular shape in plan view, the width Ha of the beam portion 12a is the same as the width Hb of the weight portion 12b, and the length Lb of the weight portion 12b is divided by The value of the sum of the length Lb of the weight portion 12b and the length La of the beam portion 12a is 0.4 or more and 0.6 or less. Thereby, the piezoelectric conversion device 1 can achieve a critical flow rate at which the fluid-induced vibration occurs, and the piezoelectric conversion efficiency can be improved.

The first modification of the piezoelectric transducer 1 of the present embodiment is different from the configuration of FIG. 1 in that, for example, the inclined portion 10e is provided on the opposing portion 11b, and the protruding portion 12c and the opposing portion 11b are provided. The distance is longer. The opposing portion 11b is provided with an inclined surface 10e between the opposing surface facing the supporting portion 11a and the one surface of the opposing portion 11b in the thickness direction. As a result, in the piezoelectric transducer 1 of the first modification, since the inclined surface 10e is provided in the opposing portion 11b, the fluid flow path 15 can be more efficiently flowed, and the fluid energy can be raised to the vibration region. The conversion efficiency of the vibration energy of the block 12. Therefore, the piezoelectric conversion device 1 of the first modification can improve the conversion efficiency from the fluid energy to the electric energy.

The second modification of the piezoelectric transducer 1 of the present embodiment is different from the configuration of FIG. 1 in the following points: in the vibration block 12, the beam is separated from the beam in both directions of the thickness direction of the weight portion 12b. A concave portion 12bb is formed on the surface of the portion 12a. Thereby, compared with the configuration of FIG. 1, in the piezoelectric transducer 1 of the second modification, the natural frequency of the vibration block 12 can be increased, and vibration can be performed in accordance with the fluid energy having a relatively high flow velocity. Further, the shape of the concave portion 12bb is not particularly limited. Further, the number of the concave portions 12bb is not limited to one, and may be plural.

In the second modification of the piezoelectric conversion device 1, as shown in FIG. 11, the inventor of the present invention defines a width of the beam portion 12a in a plan view in a state where the vibration block 12 is not warped, and the weight portion is The width of 12b is Hb, the length of the beam portion 12a is La, and the length of the weight portion 12b is Lb as a structural parameter of the vibration block 12.

Fig. 12 shows the vibration of the second modification of the piezoelectric transducer 1 when the width Ha of the beam portion 12a and the width Hb of the weight portion 12b are the same, and the ratio R of the weight portion 12b is 50%. The measurement result of the characteristic. In Fig. 12, the horizontal axis represents the flow velocity of the fluid, and the vertical axis represents the amplitude of the vibration block 12. The resonant frequency of the vibrating block 12 is 275 Hz. The second modification of the piezoelectric transducer 1 that obtains the vibration characteristics of FIG. 12 is the same as the width H of the tie beam portion 12a and the width Hb of the weight portion 12b, and the piezoelectric transducer 1 that obtains the vibration characteristics of FIG. La+Lb is also the same.

In the second modification, it is also known that the ratio R of the weight portion 12b is set to 50% in the same manner as in the piezoelectric transducer 1 of the first embodiment, and the amplitude tends to increase as the flow velocity increases. As is clear from the results of FIG. 5 to FIG. 7 and FIG. 12, even if the critical flow rate of the resonance frequency and the fluid-induced vibration changes due to the presence or absence of the concave portion 12bb, the amplitude can be made as long as the ratio R of the weight portion 12b is 50%. As the flow rate increases, the piezoelectric conversion efficiency can be improved.

Further, when the vibration characteristics of the measurement results shown in FIGS. 4 to 7 and FIG. 12 were evaluated, an experiment using a cylindrical wind tunnel was performed. The wind tunnel has an inner diameter of 0.1 m and a length of 2 m. In the experiment, the piezoelectric transducer 1 was placed in the vicinity of the outlet of the wind tunnel in the wind tunnel, and a fan was used to flow the airflow from the inflow side of the wind tunnel. In this experiment, the piezoelectric conversion device 1 was fixed such that the support portion 11 was perpendicular to the flow field, and the amplitude of the vibration block 12 was measured by a laser Doppler vibration displacement meter. Also in this experiment, the flow rate of the fluid is changed by a fan.

In the piezoelectric transducer 1 of the first modification, the recess 12bb of the piezoelectric transducer 1 of the second modification may be provided in the weight portion 12b.

When the piezoelectric conversion device 1 is used as a power generation device, for example, a power source such as an actuator, a sensor, a solid-state light-emitting element, a wireless communication element, an arithmetic element, or the like can be used. In addition, as far as the sensor is concerned, there are, for example, a temperature sensor, an acceleration sensor, a pressure sensor, and the like. Examples of the solid-state light-emitting element include a light-emitting diode and a semiconductor laser. The arithmetic element includes, for example, an MPU (Micro Processor Unit) or the like.

(Embodiment 2)

The piezoelectric transducer 1 of the present embodiment will be described below with reference to Fig. 13 . The piezoelectric transducer 1 of the present embodiment differs in that the opposing portion 11b is provided with a second protruding portion 13 that protrudes toward the protruding portion 12c, that is, the first protruding portion 12c, and the second protruding portion 13 faces the first one. The opposite side of the protruding portion 12c is warped. The same components as those in the first embodiment are denoted by the same reference numerals and will not be described.

In the piezoelectric transducer 1 of the first embodiment, the insulating layer 18a composed of the yttrium oxide film described in the first embodiment is not formed on the ruthenium layer 10c in the opposing portion 11b, but is a tantalum nitride film. The insulating film 18c is formed.

The second protruding portion 13 is composed of a third ruthenium layer 10cd, a portion constituting the second protrusion portion 13 among the ruthenium layer 10c, and a third insulating film 18cc formed in the third layer of the insulating film 18c. A portion on one side in the thickness direction of the layer 10cd. The second protruding portion 13 is warped by the internal stress, that is, the tensile stress of the third insulating film 18cc. The internal stress of the insulating film 18c can be controlled by, for example, setting a process condition such as a gas pressure or a temperature when the insulating film 18c is formed by a sputtering method or a CVD method.

In the piezoelectric transducer 1 of the present embodiment, by providing the second projecting portion 13, the fluid can flow more efficiently in the flow path 15, and the vibration energy from the fluid energy to the vibration block 12 can be increased. Conversion efficiency. Therefore, the piezoelectric conversion device 1 of the first modification can improve the conversion efficiency from the fluid energy to the electric energy.

In the piezoelectric transducer 1 of the present embodiment, the concave portion 12bb of the piezoelectric transducer 1 according to the second modification of the first embodiment can be provided in the weight portion 12b.

(Embodiment 3)

The flow rate sensor A1 of the present embodiment will be described below with reference to Fig. 14 .

The flow sensor A1 includes: the piezoelectric conversion device 1 of the first embodiment; and the detecting unit 2, An electric signal output from the piezoelectric conversion portion 14 of the piezoelectric conversion device 1 is detected. The electric signal output from the piezoelectric conversion portion 14 is an alternating voltage generated by the piezoelectric conversion portion 14.

The AC voltage generated by the piezoelectric conversion portion 14 becomes a sinusoidal waveform AC voltage in response to the vibration of the vibration block 12. The piezoelectric transducer 1 generates self-induced vibration by the pressure difference on both sides in the thickness direction of the protruding portion 12c generated by the flow of the fluid passing through the flow path 15, and the elasticity of the vibration block 12, and can respond to An alternating voltage at which the absolute value of the peak voltage changes depending on the flow rate or flow rate of the fluid.

The electric signal detected by the detecting unit 2 includes, for example, a peak value or a frequency of an alternating current voltage generated by the piezoelectric converting unit 14.

The detecting unit 2 can be configured by, for example, a peak hold circuit (peak voltage detection circuit) that detects the absolute value of the peak voltage of the AC voltage output from the piezoelectric conversion unit 14, a control circuit that controls the peak hold circuit, and the like. The peak hold circuit may be configured to include a rectifier circuit, a capacitor that holds the maximum value of the output of the rectifier circuit, a reset circuit that discharges the charge held by the capacitor, a control unit that controls the reset circuit, and the like.

Thereby, the detecting unit 2 can intermittently detect the absolute value of the peak voltage of the AC voltage generated by the piezoelectric conversion unit 14. The detecting unit 2 may constitute a control unit by, for example, a microcomputer equipped with an appropriate program, and the control unit may have a memory for storing a table having the absolute value and flow rate of the AC voltage generated by the piezoelectric converting unit 14. Correspond in advance.

Here, the absolute value of the peak value of the alternating current voltage generated by the piezoelectric conversion portion 14 increases as the flow velocity of the fluid increases. Fig. 15 is a diagram showing an example of the correlation between the generated voltage and the flow rate constituted by the absolute value of the peak value of the alternating voltage. In Fig. 15, correlation examples F1, F2, and F3 of each of the three types of piezoelectric transducers 1 are shown. Three types of piezoelectric transducers 1 have the same length dimension of the vibration block 12 and the width dimension of the vibration block 12. It is different. In contrast, the correlation example F1 has a smaller width dimension of the vibration block 12, and the correlation example F3 has a larger width dimension of the vibration block 12, and the width dimension of the vibration block 12 of the related example F2 is located in the correlation example F1 and Related example F3 in the middle. As can be seen from Figure 15, the pressure When the width of the vibration block 12 is increased, the electric power conversion device 1 increases the flow rate of the self-induced vibration, but the generated voltage tends to gradually increase as the flow rate increases. Therefore, the piezoelectric conversion device 1 can be used for the flow sensor A1 that detects the flow rate in a wide flow velocity range. On the other hand, when the piezoelectric transducer device 1 reduces the width dimension of the vibration block 12, the flow velocity at which the self-induced vibration starts is reduced, and the generated voltage tends to increase rapidly as the flow velocity increases. Therefore, the piezoelectric conversion device 1 can be used for the flow sensor A1 that detects the flow rate in a narrow flow velocity range. Further, when the piezoelectric transducer device 1 has a small width dimension of the vibration block 12, since the flow rate at which the generated voltage is saturated is low, it is considered to be suitable for power generation applications in which a stable generated voltage is to be maintained.

Further, as shown in FIG. 16, the frequency of the alternating voltage generated by the piezoelectric transducer 14 decreases as the fluid flow rate increases. It is presumed that since the flow velocity of the fluid increases, the pressure on one side of the vibration block 12 increases, and the frequency at which the vibration block 12 vibrates decreases. The relationship between flow rate and frequency is almost linear. Further, the frequency of the alternating voltage generated by the piezoelectric converting portion 14 can be detected by, for example, a voltage-frequency converting circuit. At this time, the detecting unit 2 may have a memory in which the control unit has a memory table that has previously matched the frequency of the AC voltage generated by the piezoelectric converting unit 14 with the flow rate. A table in which the frequency of the alternating voltage has been previously associated with the flow rate has been used, for example, using the information of FIG.

The flow sensor A1 described above includes a piezoelectric transducer 1 in which a piezoelectric transducer 14 is provided in a vibration block 12 that is subjected to self-induced vibration while receiving a fluid, and a detecting portion 2 that detects the piezoelectric transducer 14 output electrical signals. In this flow sensor A1, since it is not necessary to supply electric power to the piezoelectric conversion portion 14 for sensing fluid, low power consumption can be achieved compared to the thermal flow sensor described in Document 2. Chemical. In the flow rate sensor A1, the piezoelectric transducer 1 having the piezoelectric transducer 14 is provided in the vibration block 12 that is subjected to self-induced vibration while receiving a fluid, and is compared with the power generating mechanism described in Document 3. Words can be miniaturized. Thereby, the flow sensor A1 can achieve low power consumption and miniaturization. Moreover, the flow sensor A1 can reduce the maintenance frequency and cost by achieving low power consumption.

Further, the flow sensor A1 can convert the energy of the fluid passing through the flow path 15 into the vibration energy of the vibration block 12 in the piezoelectric conversion device 1 in a highly efficient manner. Therefore, the flow sensor A1 It can improve the detection accuracy of fluid flow rate and flow rate.

As in the first modification shown in FIG. 17, the flow rate sensor A1 may include a wireless transmission unit 6 that intermittently transmits a wireless signal including the detection result of the detection unit 2. Thereby, the flow sensor A1 can intermittently transmit the wireless signal including the detection result of the detecting unit 2. Therefore, the flow sensor A1 can increase the degree of freedom of the installation place and improve the versatility. Further, in the gas flu detector using the plurality of flow sensors A1, the distribution of the airflow state can be investigated by appropriately configuring the plurality of flow sensors A1. In addition, as for the wireless communication standard of the wireless transmission unit 6, for example, EnOcean (registered trademark), Zigbee (registered trademark), Bluetooth (registered trademark), specific low-power radio, weak radio, Wi-Fi (registered trademark) can be used. UWB (Ultra Wide Band) is not particularly limited.

Fig. 18 is a schematic configuration diagram of an air conditioning management system using the flow sensor A1. The flow rate sensor A1 in the air conditioning management system includes a power storage unit 5 that rectifies and stores an AC voltage generated by the piezoelectric conversion device 1, and a switching circuit 9.

The switching circuit 9 is configured to be switchable in a state in which the piezoelectric conversion unit 14 and the power storage unit 5 are electrically connected to each other, and in a second state, the piezoelectric conversion unit 14 is electrically connected to the detection unit 2. In other words, the piezoelectric conversion unit 14 is connected to the switching circuit 9, and the switching circuit 9 switches between the piezoelectric transducer 14 and the power storage unit 5 in the first state, and the second state to make the voltage The electrical conversion unit 14 is electrically connected to the detecting unit 2 . Further, the detecting unit 2 and the wireless transmitting unit 6 can operate using the power storage unit 5 as a power source.

The flow rate sensor A1 preferably includes a switching element 8, a power supply path provided from the power storage unit 5 to the detecting unit 2 and the wireless transmission unit 6, and a power storage amount monitoring unit 7 that monitors the amount of stored electricity of the power storage unit 5. The switching element 8 can be formed, for example, by a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or the like. The electric storage amount monitoring unit 7 has a function of monitoring the voltage between the output terminals of the electric storage unit 5 as the electric storage amount, and turning on and off the switching element 8 based on the comparison between the electric storage amount and a predetermined value set in advance. For example, the amount of electric power stored in the power storage unit 5 reaches the drive for detecting the detection unit 2 and the wireless transmission unit 6 in advance. After the predetermined amount is set, the switching element 8 is turned on. The electric storage amount monitoring unit 7 turns off the switching element 8 after being lower than the above-described predetermined amount. Thereby, the detecting unit 2 and the wireless transmission unit 6 are intermittently subjected to power supply from the power storage unit 5 and driven.

The switching circuit 9 may be, for example, controlled to be turned on or off by the stored electricity amount monitoring unit 7. Here, the electric storage amount monitoring unit 7 may switch the switching circuit 9 from the first state to the second state when the electric storage amount of the electric storage unit 5 reaches the predetermined value.

By including the switching circuit 9, the flow rate sensor A1 can shorten the time until the amount of electric power stored in the power storage unit 5 reaches the predetermined value every time the power storage unit 5 is charged.

The power storage unit 5 can be configured, for example, by a full-wave rectifier circuit including a diode bridge that rectifies an AC voltage generated by the piezoelectric transducer 1, and a capacitor connected to the full-wave rectifier circuit. Between the outputs. At this time, the flow sensor A1 connects the output end of one side of the piezoelectric conversion device 1 to the input end of one side of the full-wave rectifying circuit, and connects the output end of the other side of the piezoelectric conversion device 1 to the full-wave rectifying circuit. The other end of the input terminal and the wireless transmission unit 6 may be connected between the two ends of the capacitor.

The power storage unit 5 can be configured by, for example, a full-wave voltage doubler rectifier circuit. The full-wave voltage-stabilizing circuit can be configured, for example, by connecting a series circuit of two diodes in parallel with a series circuit of two capacitors. In other words, the full-wave voltage doubler rectifier circuit can be configured by bridging two diodes and two capacitors. In the case where the power storage unit 5 is a full-wave voltage doubler rectifier circuit, the flow rate sensor A1 is connected to the connection point of the two diodes of the two series circuit of the two diodes by the output terminal of the piezoelectric transformer device 1 and The output terminal of the other side of the piezoelectric conversion device 1 may be connected to a connection point of two capacitors in a series circuit of two capacitors. Further, the flow rate sensor A1 may connect the detecting unit 2 and the wireless transmission unit 6 to both ends of a series circuit of two capacitors.

The air conditioning management system includes: a flow sensor A1; and an air conditioner A2. The flow sensor A1 is disposed inside an air supply duct (not shown) or an exhaust duct (not shown) of the air conditioner A2.

The air conditioner A2 includes a wireless receiving unit 71 that receives a wireless signal from the wireless transmitting unit 6, and a control unit 72 that controls the operating state of the fan 74 based on the wireless signal received by the wireless receiving unit 71 to cause a flow rate or a flow rate of the fluid. Become the target value. In this way, since the air-conditioning management system includes the flow rate sensor A1 that can be reduced in power consumption and miniaturization, it is possible to achieve low power consumption of the entire air-conditioning management system.

The air conditioner A2 includes a motor 73 that rotates the fan 74, an operation switch 75, a control unit 72 that controls the operation state of the fan 74 by controlling the motor 73, and a setting unit 76 that sets the flow rate based on a remote control signal or the like from the remote controller. Or the target value of the flow rate. The air conditioner A2 is turned on by the operation switch 75, so that the control unit 72 drives the motor 73 to rotate the fan 74. The control unit 72 feedbacks the rotational speed of the motor 73 to be the target value of the flow rate or the flow rate set by the setting unit 76. Thereby, the air conditioning management system can achieve energy saving. In addition, the control unit 72 may include, for example, a control circuit including a microcomputer or the like equipped with an appropriate program, a drive circuit for driving the motor 73, and the like.

The second modification of the flow rate sensor A1 of the present embodiment is different from the configuration of the piezoelectric conversion device 1 as shown in Fig. 19, for example. In the piezoelectric transducer 1 of the flow rate sensor A1 of the second modification, the piezoelectric transducer 14 includes a first piezoelectric transducer 141 and a second piezoelectric transducer 142. The first piezoelectric conversion unit 141 is connected to the power storage unit 5 . The second piezoelectric conversion unit 142 is connected to the detection unit 2 .

In the piezoelectric transducer 1 described in the first embodiment, two piezoelectric transducers 14 are arranged side by side in the width direction of the beam portion 12a, and each of the piezoelectric transducers 14 is provided. 1 pad electrode 17a and second pad electrode 17c. In this case, the piezoelectric conversion unit 14 on one side may be the first piezoelectric conversion unit 141, and the piezoelectric conversion unit 14 on the other side may be the second piezoelectric conversion unit 142.

The flow rate sensor A1 according to the second modification includes the first piezoelectric conversion unit 141 connected to the power storage unit 5 and the second piezoelectric conversion unit 142 connected to the detection unit 2, so that it can be configured by a simple circuit. The detecting unit 2 is used to detect an electrical signal output from the piezoelectric conversion unit 14.

In addition, the number of the piezoelectric transducers 14 is not limited to two, and may be three or more, and may include at least one of the first piezoelectric transducer 141 and the second piezoelectric transducer 142. Further, the flow rate sensor A1 may be configured such that the piezoelectric transducer 1 having one piezoelectric transducer 14 is provided in parallel.

Each of the drawings described in the first embodiment, the second embodiment, and the like is schematically illustrated, and the ratio of the size or thickness of each component does not necessarily reflect the size ratio of the physical object.

In the above, the configuration of the present invention is described with reference to the first embodiment to the third embodiment, and the present invention is not limited to the configuration of the first embodiment to the third embodiment. For example, the partial configuration of the first embodiment to the third embodiment may be employed. Constructed by appropriate combination. Further, the materials, numerical values, and the like described in the first to third embodiments are merely preferred, and are not limited thereto. Furthermore, the present invention can be modified as appropriate without departing from the scope of the technical idea.

1‧‧‧Piezoelectric conversion device

10‧‧‧Substrate

10a‧‧‧矽 substrate

10b‧‧‧ buried oxide film

10c‧‧‧ layer

10ca‧‧‧1st floor

10cc‧‧‧2nd layer

10d‧‧‧slit

10f‧‧‧ space

11‧‧‧Framework

11a‧‧‧Support Department

11b‧‧‧ opposite department

11c‧‧‧Link Department

12‧‧‧Vibration block

12a‧‧ ‧ Beam Department

12b‧‧‧weight department

12c‧‧‧ highlights

12cc‧‧‧ front end

14‧‧‧Piezoelectric conversion department

14a‧‧‧1st electrode (lower electrode)

14b‧‧‧piezoelectric layer

14c‧‧‧2nd electrode (upper electrode)

15‧‧‧ flow path

16a‧‧‧1st wiring

16c‧‧‧2nd wiring

17a‧‧‧1st pad electrode

17c‧‧‧2nd pad electrode

18a‧‧‧Insulation film

18aa‧‧‧1st insulating film

18ac‧‧‧2nd insulation film

19‧‧‧Insulation

Claims (11)

A piezoelectric conversion device comprising: a support portion; an opposite portion opposite to the support portion; and a vibration block located between the support portion and the opposite portion, one end of which is fixed to the support portion, The other end is spaced apart from the opposite portion; and the vibration block includes: a beam portion thinner than the support portion, supported by the support portion to swing freely; and a weight portion disposed at a front end of the beam portion, thicker than the a beam portion; the protruding portion protrudes toward a side opposite to the beam portion side, and is thinner than the weight portion and the opposite portion; and the piezoelectric conversion portion generates an alternating current in response to vibration of the beam portion a voltage; and the normal portion of the vibrating block that is turned into the front end surface of the protrusion does not intersect the opposite portion. The piezoelectric transducer of claim 1, wherein the natural frequency of the protrusion is greater than a natural frequency of the vibration block. The piezoelectric transducer according to claim 1, wherein the opposing portion is provided with an inclined surface between the opposing surface facing the supporting portion and a surface in the thickness direction of the opposing portion, the inclined portion The face lengthens the distance between the protrusion and the opposing portion. The piezoelectric transducer according to claim 1, wherein the opposing portion is provided with a second protruding portion that protrudes toward the first protruding portion side of the protruding portion, and the second protruding portion faces the first protruding portion The opposite side is warped. The piezoelectric transducer according to claim 1, wherein the vibration block is formed with a concave portion on a surface farther from the beam portion of the two faces in the thickness direction of the weight portion. The piezoelectric transducer according to claim 1, wherein the beam portion is configured by: a first layer; and a first insulating film formed on one surface side in a thickness direction of the first layer; And having a compressive stress; and being warped by the compressive stress of the first insulating film, the protruding portion is configured by: a second germanium layer; and a second insulating film formed on the second germanium layer One side in the thickness direction has a compressive stress; and warps by the compressive stress of the second insulating film. The piezoelectric transducer according to claim 4, wherein the beam portion is composed of: a first layer; and a first insulating film formed on one surface side in a thickness direction of the first layer; And having a compressive stress; and the warp is warped by the compressive stress of the first insulating film, the first protruding portion is configured by: a second layer; and a second insulating film formed on the second layer One side of the layer in the thickness direction has a compressive stress; and the second insulating film is warped by the compressive stress of the second insulating film, and the second protruding portion is composed of a third layer; and a third insulating film. It is formed on one surface side in the thickness direction of the third layer, and has a tensile stress; and is warped by the tensile stress of the third insulating film. The piezoelectric conversion device of claim 1, wherein the vibration block has a rectangular shape in plan view, and the width of the beam portion is the same as the width of the weight portion, and the length of the weight portion is divided by the The value obtained by the sum of the length of the heavy portion and the length of the beam portion is 0.4 or more and 0.6 or less. A flow sensor comprising: the piezoelectric conversion device according to claim 1; and a detecting portion that detects an alternating voltage generated by the piezoelectric conversion portion. The flow sensor of claim 9 is characterized in that: the wireless transmission unit intermittently performs transmission of a wireless signal including the detection result of the detection unit. The flow sensor of claim 10, comprising: a power storage unit that rectifies and stores an AC voltage generated by the piezoelectric conversion unit; and a switching circuit; and the switching circuit is configured to be in a state of the following Switching between: the first state, the piezoelectric conversion unit is electrically connected to the power storage unit; and the second state, the piezoelectric conversion unit is electrically connected to the detection unit; and the detection unit and the wireless The transmission unit can operate the power storage unit as a power source.