JP5549164B2 - Piezoelectric generator - Google Patents

Description

  The present invention relates to a piezoelectric generator that generates electricity using a piezoelectric material.

  In recent years, in order to maintain and improve the global environment, research and development of power generation devices with a low environmental load has been actively conducted. Among them, there is a power generator that converts mechanical energy generated by natural forces or artificial forces or vibrations into electrical energy to convert energy that is normally unconsciously and wasted into electrical energy and uses it as a power source. Is provided.

As a device for converting mechanical energy into electrical energy, a method using a piezoelectric body has been proposed.
With regard to this type of technology, Patent Document 1 discloses a piezoelectric power generation in which one end of a plate spring-like cantilever having a plate-like piezoelectric body joined to the surface is fixed to a housing and a weight is provided at the other end which is a free end. The machine is listed.
Further, in Patent Document 2, a plate spring-like cantilever beam having a weight at the free end is sandwiched between a pair of piezoelectric bodies from the front and back, and electric power generated every half cycle of vibration is continuously taken out. A piezoelectric generator is described.

JP-A-2005-45588 JP 2005-31269 A

  However, since the piezoelectric material constituting the piezoelectric body generally has extremely high rigidity, the swing deformation of the vibrating body to which the piezoelectric body is bonded is suppressed. For this reason, when the size of the device is reduced in consideration of portability, using vibrations during walking of humans and animals, and driving vibrations of automobiles, bicycles, etc. as described in Patent Documents 1 and 2. It was difficult to obtain sufficient power generation efficiency with a piezoelectric generator.

  The present invention has been made in view of the above problems, and provides a piezoelectric generator capable of improving both portability and power generation efficiency while using vibration during walking or running as a drive source. .

A piezoelectric generator according to the present invention includes a housing and a piezoelectric power generation unit that is fixed to the housing and generates power by stress generated by reciprocal swinging with respect to the housing, and the resonance frequency of the power generation unit is 10 Hz. A vibration body having a plurality of vibration elements that are curved strip-shaped flat plates, and the power generation unit includes a plurality of the vibration elements whose base ends are fixed to the housing; A piezoelectric body that is joined to at least one main surface of each of the plurality of vibrating element pieces and swings together with the plurality of vibrating element pieces, and the plurality of vibrating element pieces are formed on the main surface. A common weight that reciprocally swings in the direction perpendicular to the surface is mounted, and the curved shape that curves in the plane direction of the main surface is formed and fitted adjacent to each other on the same plane . .

Further, in the piezoelectric generator of the present invention, as a more specific embodiment, the planar view shape of the plurality of vibrating element pieces viewed in the direction perpendicular to the main surface is substantially the whole except for the vicinity of the base end portion. The piezoelectric body is bonded to at least one main surface of the plurality of vibrating element pieces, and each of the plurality of vibrating element pieces has respective base ends attached to the casing. The weight may be fixed to the tip and the common weight may be attached to the tip.

A piezoelectric generator of the present invention is also a more specific embodiments of implementation, a plurality of said vibration piece is a spiral-shaped adjacent to each other on said same plane, the weight is, the center of the spiral shape Disposed, the tips of the plurality of vibrating elements are fixed at positions displaced around the weight, and the plurality of vibrating elements extend in a common spiral direction around the weight. Good.

  Note that the various components of the present invention do not have to be individually independent, that a plurality of components are formed as one member, and one component is formed of a plurality of members. It may be that a certain component is a part of another component, a part of a certain component overlaps a part of another component, and the like. In particular, the vibrating body and the piezoelectric body may be configured as separate members, or may be a common member. That is, when generating electricity with a so-called unimorph-type or bimorph-type piezoelectric element, it is preferable to use a piezoelectric body, which is a separate member, and a vibrating body such as metal. On the other hand, when power is generated by a so-called monopolar piezoelectric element, the vibrating body and the piezoelectric body may be formed of a common member.

  According to the piezoelectric generator of the present invention, since the resonance frequency of the vibrating body is 10 Hz or less, the vibrating body can be used even when the driving source is vibration during walking of a human or animal, or traveling vibration of an automobile or bicycle. Therefore, portability and high power generation efficiency can be obtained.

It is a perspective view which shows an example of the piezoelectric generator of 1st embodiment. (A) is a top view of the piezoelectric generator of 1st embodiment, (b) is the BB sectional drawing. (A) is a longitudinal sectional view of a unimorph type piezoelectric element, and (b) and (c) are longitudinal sectional views of a bimorph type piezoelectric element. (A)-(c) is an elevation model which shows a mode that a piezoelectric element carries out rocking deformation. It is a top view of the piezoelectric generator of a second embodiment. It is a perspective view which shows an example of the piezoelectric generator of 3rd embodiment. (A) is a top view of the piezoelectric generator of 3rd embodiment, (b) is BB sectional drawing of (a), (c) is CC sectional drawing of (b). It is an enlarged view of Fig.7 (a) regarding the vicinity of a piezoelectric material. (A) is sectional drawing which cut the piezoelectric material in the height direction, (b) is a deformation | transformation figure at the time of pressing a piezoelectric material in the height direction. (A) is a top view of the piezoelectric generator of 4th embodiment, (b) is the BB sectional drawing. (A) is a top view of the piezoelectric generator of 5th embodiment, (b) is the BB sectional drawing, (c) is CC sectional drawing of (b). 6 is a plan view of a piezoelectric generator according to Comparative Example 1. FIG. (A) is a top view of the piezoelectric generator concerning the comparative example 2, (b) is the BB sectional drawing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, the same reference numerals are given to the same components, and the description will be omitted as appropriate.

<First embodiment>
FIG. 1 is a perspective view showing an example of the piezoelectric generator 10 of the present embodiment.
2A is a plan view of the piezoelectric generator 10 with the housing lid 60 removed, and FIG. 2B is a cross-sectional view taken along the line BB in FIG.

First, the outline | summary of the piezoelectric generator 10 of this embodiment is demonstrated.
The piezoelectric generator 10 includes a housing 30 and a piezoelectric power generation unit 40.
The power generation unit 40 is a device that is fixed to the housing 30 and generates power by stress generated by reciprocal swinging with respect to the housing 30.
In the piezoelectric generator 10 of the present embodiment, the resonance frequency of the power generation unit 40 is 10 Hz.

Hereinafter, the piezoelectric generator 10 of this embodiment will be described in detail. For convenience, the vertical direction in FIG. 2A is referred to as the longitudinal direction of the piezoelectric generator 10 and the vibrating body 20, and the horizontal direction in FIG. The longitudinal direction and the width direction may be collectively referred to as the plane direction of the piezoelectric generator 10.
Moreover, the up-down direction of FIG.2 (b) is called thickness direction or planar view direction. In the present embodiment, the swinging direction of the vibrating body 20 is the thickness direction of the piezoelectric generator 10.
In addition, regarding each component of the piezoelectric generator 10 including the vibrating body 20, when expressed as “shape” without any notice, it means a shape in plan view.

Here, the plane direction and the thickness direction are defined for convenience in order to briefly explain the relative relationship of the constituent elements of the piezoelectric generator 10, and the directions at the time of manufacture and use of the piezoelectric generator 10 are defined. It is not limited.
That is, the piezoelectric generator 10 of the present embodiment swings the power generation unit 40 in the thickness direction by applying an acceleration load to the housing 30, but the thickness direction of the housing 30 does not necessarily match the gravity direction. There is no need to let them. Of the external force applied to the housing 30, the power generation unit 40 can be swung by the thickness direction component of the housing 30.

In the present embodiment, the power generation unit 40 is exemplified by a unimorph type or bimorph type piezoelectric element in which a piezoelectric body 42 made of a piezoelectric material and a conductive electrode film 44 are joined to the main surface of the metallic vibrating body 20. .
That is, the power generation unit 40 of this embodiment is joined to at least one main surface of the vibrating body 20 with the base end 24 fixed to the housing 30 and swings together with the vibrating body 20. And a piezoelectric body 42. Then, when the vibrating body 20 reciprocally swings in the direction perpendicular to the surface, a tensile state and a compressed state are alternately generated on the front and back surfaces of the vibrating body 20. The tensile stress and the compressive stress are transmitted to the piezoelectric body 42 bonded to the main surface of the vibrating body 20 to distort the piezoelectric body 42, and an electromotive force is generated in the piezoelectric body 42 by the piezoelectric power generation effect.
In the present embodiment, the base end portion 24 of the vibrating body 20 is a predetermined length in which the vibrating body 20 is supported directly on the housing 30 or indirectly through other members. The end region of the vibrating body 20 is not necessarily included.

  In the present invention, as in third to seventh embodiments to be described later, the power generation unit 40 may have a piezoelectric body 42 sandwiched between the base end portion 24 of the vibrating body 20 and the housing 30. .

  The dimensions and the size of the piezoelectric generator 10 in the width direction and the longitudinal direction are not particularly limited, but the casing 30 of the present embodiment has a rectangular shape in plan view, more specifically, a substantially square shape, and the width dimension. And the longitudinal dimension are substantially equal to each other and are about several millimeters to several centimeters.

  As shown in FIGS. 1 and 2, the external structure of the piezoelectric generator 10 includes a housing 30, a housing lid 60 that covers the opening of the housing 30, and an external device that is exposed outside the housing 30. Electrode 70.

  The housing | casing 30 is a container which accommodates the electric power generation unit 40 so that a reciprocating rocking | fluctuation is possible inside. The housing 30 has a box shape with an open upper surface, and a pair of block-shaped bases 32 are provided upright at two opposing corners inside the hollow.

The base 32 is a base that supports both ends of the power generation unit 40. The power generation unit 40 is installed in a state where both ends are fixedly supported with respect to the pair of bases 32.
The upper surface of the base 32 and the thickness center of the plate-shaped power generation unit 40 of the present embodiment are at a substantially intermediate depth inside the hollow of the housing 30.

The vibrating body 20 of the present embodiment is a metal substrate that constitutes the power generation unit 40 with a piezoelectric body 42 bonded to one or both of its main surfaces. The vibrating body 20 also functions as a metal electrode for sending the alternating current generated by the piezoelectric body 42 to the external electrode 70.
The metal material which comprises the vibrating body 20 is not specifically limited, Stainless steel and phosphor bronze can be illustrated. In addition to the metal material, the vibrating body 20 may be a resin plate or a conductive resin plate plated on one or both sides. Furthermore, a conductive resin can also be used.
The vibrating body 20 has predetermined flexibility and bending rigidity in the perpendicular direction. For this reason, when an acceleration load is applied to the housing 30 and a relative speed is generated between the housing 30 and the weight 50 due to the inertial force of the weight 50, the vibrating body 20 that supports the weight 50 will thereafter be the housing 30. Reciprocally oscillates relative to.

As shown in FIG. 2A, the vibrating body 20 of the present embodiment has a curved plate shape.
More specifically, the vibrating body 20 (power generation unit 40) has a plate shape that is a spiral shape in plan view.
The spiral shape of the vibrating body 20 (power generation unit 40) is a two-turn equidistant spiral (Archimedes spiral). The curved shape of the vibrating body 20 (power generation unit 40) may be a spiral shape, a waveform, a key shape, a sawtooth shape, or the like.

The vibrating body 20 includes a plurality of vibrating element pieces 21 and 22 each having a spiral plate shape in plan view.
A piezoelectric body 42 and an electrode film 44 (see FIG. 3) are joined to substantially the entire surface of at least one main surface of the vibrating element pieces 21 and 22.
Each of the vibrating element pieces 21 and 22 has one base end portion 24 fixed to the housing 30, and a common weight 50 is attached to the tip end portion 25.

The vibrating element pieces 21 and 22 have spiral shapes adjacent to each other on the same plane, and the respective tips are fixed to the weight 50. The vibrating elements 21 and 22 are respectively equally spaced spirals.
The vibration element pieces 21 and 22 of the present embodiment are manufactured as a series of spiral belt-like members, and are formed radially around the weight 50. That is, it is not essential that the vibrating elements 21 and 22 are made of different members.

The vibrating elements 21 and 22 are curved in a common spiral direction around the weight 50. Further, the vibrating elements 21 and 22 are provided at rotationally symmetrical positions by 180 degrees in the longitudinal direction with the weight 50 interposed therebetween.
The base end portions 24a and 24b of the vibrating element pieces 21 and 22 are formed linearly along the side of the casing 30 that is rectangular in plan view. The base end portions 24 a and 24 b are fixed to the pair of bases 32, respectively. The base end portions 24a and 24b and the base 32 are fixed to each other.

  The power generation unit 40 of the present embodiment is obtained by laminating a piezoelectric body 42 and an electrode film 44 on at least one of the main surfaces of the vibrating element pieces 21 and 22. Therefore, the power generation unit 40 is a both-end support beam that is fixedly supported by the housing 30 at both ends and receives the concentrated load of the weight 50 at the center.

  The weight 50 is bonded to both the front and back surfaces of the central part of the spiral of the vibrating element pieces 21 and 22. The weight, shape, dimensions, and the like of the weight 50 are adjusted so that the resonance frequency of the power generation unit 40 supported at both ends by the base 32 is 10 Hz or less.

3A to 3C are longitudinal sectional views of the power generation unit 40. FIG. FIG. 6A is a longitudinal sectional view of a unimorph type power generation unit 40 in which a piezoelectric body 42 is bonded to one main surface (upper surface in the drawing) of a vibrating body 20 that is a metal plate-like body. FIGS. 7B and 7C are longitudinal sectional views of a bimorph type power generation unit 40 in which plate-like piezoelectric bodies 42 are joined to both main surfaces of the vibrating body 20.
An electrode film 44 that is a conductive thin film is laminated on the surface of the piezoelectric body 42 of the power generation unit 40.

As the piezoelectric material constituting the piezoelectric body 42, for example, a ferroelectric having a perovskite crystal structure can be used. As an example, barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ), lead zirconate titanate (Pb (ZR, Ti) O ₃ ), lead lanthanum zirconate titanate ((Pb, La) (Zr, Ti) O ₃ ).

  The piezoelectric body 42 and the vibrating body 20 are adhesively bonded by a thermosetting adhesive such as an epoxy adhesive applied extremely thinly. Further, the piezoelectric body 42 is polarized in the thickness direction as indicated by arrows in each drawing of FIG.

When the vibrating body 20 is reciprocally swung in the perpendicular direction with one or both ends of the power generation unit 40 fixed as described above, the piezoelectric body 42 alternately receives tensile stress or compressive stress, and in-plane direction. Extends and contracts. Thereby, an alternating electromotive force is generated in the piezoelectric body 42 between the front and back surfaces corresponding to both end faces in the polarization direction.
The electrode film 44 and the vibrating body 20 are individually connected to the external electrode 70a or the external electrode 70b, respectively. FIGS. 3A to 3C show a method for extracting an alternating current. Specifically, in the case of the unimorph type power generation unit 40 in FIG. 3A, alternating currents having opposite phases are generated from the electrode film 44 corresponding to the positive direction of the polarization direction of the piezoelectric body 42 and the vibrating body 20 corresponding to the negative direction. The output is connected to the external electrodes 70a and 70b.
In the bimorph type power generation unit 40 in FIG. 3B, the polarization directions of the pair of piezoelectric bodies 42 sandwiching the vibrating body 20 are opposite to each other. Specifically, the piezoelectric body 42t on the upper surface side of the vibrating body 20 is polarized from the upper surface side toward the lower surface side, and the polarization direction of the piezoelectric body 42b on the lower surface side of the vibrating body 20 is reversed. Here, since tension and compression occur oppositely on the upper surface and the lower surface of the vibrating body 20 that reciprocally vibrate, the piezoelectric body 42t on the upper surface side and the piezoelectric body 42b on the lower surface side of the vibrating body 20 are at the antinode of reciprocal vibration. One is compressed in the in-plane direction and increased in the thickness direction (polarization direction), and the other is pulled and decreased in the thickness direction (polarization direction). That is, the piezoelectric body 42t and the piezoelectric body 42b whose polarization directions are opposite to each other are positive and negative in displacement in the thickness direction (polarization direction) generated in accordance with the vibration of the vibrating body 20. Accordingly, the upper and lower surfaces of the piezoelectric body 42t and the piezoelectric body 42b have the same potential. An added potential difference is generated between the electrode film 44t and the electrode film 44b corresponding to both outer surfaces of the piezoelectric body 42t and the piezoelectric body 42b connected in series. For this reason, in the power generation unit 40 of the figure, the external electrodes 70a and 70b are connected to the electrode film 44t and the electrode film 44b, respectively, and an alternating current is output.
In the bimorph type power generation unit 40 of FIG. 3C, the polarization directions of the pair of piezoelectric bodies 42 sandwiching the vibrating body 20 are common. For this reason, contrary to FIG. 3B, the reciprocating vibration of the vibrating body 20 generates potentials having the same polarity (in the same phase) in the electrode film 44t and the electrode film 44b, and the vibrating body 20 has the opposite phase. Is generated. For this reason, in the power generation unit 40 in FIG. 3C, the electrode film 44t and the electrode film 44b are connected together to one external electrode (external electrode 70a), and the vibrating body 20 is connected to the other external electrode (external electrode 70b). Connect and output alternating current.

  In the present invention, a monomorph type piezoelectric element may be used as the power generation unit 40. That is, instead of the embodiment shown in FIG. 3, a plate-like piezoelectric body 42 having a predetermined thickness made of a piezoelectric material having an electrode film as a conductive thin film formed on both sides is fixed to the housing 30 and reciprocally shaken. The metal vibrating body 20 may be excluded by moving.

Here, that the resonance frequency of the power generation unit 40 is 10 Hz or less means that application of periodic vibration of 10 Hz or less to the housing 30 causes resonance in the power generation unit 40 and generation of electromotive force in the piezoelectric body 42. Say. That is, in the case of the power generation unit 40 formed of a unimorph type or bimorph type piezoelectric element in which the piezoelectric body 42 and the electrode film 44 are laminated on the main surface of the vibrating body 20 as in the present embodiment, the primary natural frequency of the piezoelectric element. Is 10 Hz or less.
Further, when the power generation unit 40 is composed of a monomorph type piezoelectric element, the resonance frequency of the power generation unit 40 being 10 Hz or less means that the primary natural frequency of the piezoelectric body 42 is 10 Hz or less.

4A to 4C are schematic elevational views showing a state where the power generation unit 40 (piezoelectric element) is oscillated and deformed. The piezoelectric body 42 and the electrode film 44 (see FIG. 3) are not shown.
FIG. 6A shows the state of the top dead center of the vibrating body 20 that vibrates with the weight 50. The vibrating body 20 is displaced upward as indicated by an arrow from its natural state (neutral plane NP). FIG. 2B shows the antinode state of vibration of the vibrating body 20, and the vibrating body 20 coincides with the neutral plane NP. FIG. 2C shows the bottom dead center state of the vibrating body 20. The vibrating body 20 is displaced downward as indicated by an arrow from the neutral plane NP.
Then, until the vibrator 20 is displaced upward or downward from the neutral state in FIG. 5B, the bending flexure increases as a whole with the base end portion 24 as the support end. On the other hand, the bending deflection of the vibrating body 20 gradually decreases while returning to the neutral state from the top dead center of FIG.
Then, at the top dead center shown in FIG. 5A, large compression occurs on the upper surface side of the vibrating body 20, and tension occurs on the lower surface side. The opposite is true at the bottom dead center shown in FIG.
In this way, the power generation unit 40 polarized in the thickness direction (see FIG. 3) reciprocally swings, so that the electrode film 44 and the vibration are vibrated regardless of whether the power generation unit 40 is a unimorph type or a bimorph type. An electromotive force is generated between the bodies 20 (see FIG. 3).

  Hereinafter, in the piezoelectric generator 10 of the present embodiment, a unimorph type in which the electrode film 44 is attached to the surface of the piezoelectric body 42 and the vibrating body 20 is exposed as a metal electrode on the back surface will be described as an example.

The external electrodes 70 (70a, 70b) are respectively attached to the outside of the opposite sides of the housing 30.
The external electrode 70 is made of a metal material bent into an L shape, and is attached to the external side surface 30a and the external side surface 30b of the housing 30 (see FIG. 1).

Returning to FIG. 2, connection lines 72 and 73 are connected to the external electrode 70a, and connection lines 74 and 75 are connected to the external electrode 70b.
The connection line 72 and the connection line 73 are connected to the electrode film 44 laminated on the upper surface of the vibration element piece 22 and the upper surface of the vibration element piece 21, respectively.
The connection line 74 and the connection line 75 are respectively connected to the lower surface of the vibration element 22 and the lower surface of the vibration element 21.
The connection lines 72 to 75 are connected to the vicinity of the base ends 24 a and 24 b of the power generation unit 40, respectively, and prevent interference with the vibrating body 20 that reciprocally swings around the weight 50.

On the upper surface of the housing 30, groove portions 34 that guide the connection lines 72 to 75 from the inside of the housing 30 to the external electrode 70 are provided.
Instead of the groove 34, a through-hole penetrating the standing wall surface 33 of the housing 30 to which the external electrode 70 is bonded inward and outward is provided to guide the connection lines 72 to 75 from the hollow interior of the housing 30 to the external electrode 70. May be.

Connection lines 72 and 73 are joined to the upper surfaces of the vibrating elements 21 and 22, more specifically, the upper surfaces in the vicinity of the base end portions 24a and 24b, respectively, and the external electrode 70a is connected to the upper surface (electrode film) of the piezoelectric body 42. 44).
On the other hand, connection lines 74 and 75 are joined to the lower surface of the vibrating elements 21 and 22, more specifically, the lower surface near the base end portions 24a and 24b, respectively, and the external electrode 70b is connected to the lower surface ( It has the same potential as the vibrating body 20).
Then, by arbitrarily connecting a rectifier circuit or a converter (not shown) to the external electrode 70, the piezoelectric generator 10 supplies a power source for other devices and a charging current to a charger (rechargeable battery). It can be used as a generator.

Further, as shown in FIG. 2B, on the back surface of the housing lid 60 and the inner bottom surface 31 of the housing 30, a displacement stopper 62 that regulates the height positions of the top dead center and the bottom dead center of the weight 50, 36 are erected inward from each other. The displacement stoppers 62 and 36 may be provided at a plurality of locations on the housing lid 60 and the housing 30, respectively.
The displacement stopper 62 on the back surface of the housing lid 60 is in contact with the upper end surface of the weight 50 and restricts the top dead center of the power generation unit 40 to a predetermined height or less. Thereby, the power generation unit 40 does not exceed the allowable amplitude, and the piezoelectric body 42 is protected.
Further, the displacement stopper 36 on the inner bottom surface 31 of the housing 30 abuts on the lower end surface of the weight 50 and regulates the bottom dead center of the power generation unit 40 to a predetermined height or more. Thereby, the power generation unit 40 does not exceed the allowable amplitude, and the piezoelectric body 42 is protected.

  In the present invention, the power generation unit 40 is adjusted by adjusting the clearance between the lower surface of the housing lid 60 and the inner bottom surface 31 of the housing 30 and the power generation unit 40 without providing the displacement stoppers 62 and 36. May be prevented from exceeding the allowable amplitude. Thereby, the tensile or compressive stress applied to the piezoelectric body 42 is suppressed to the fracture limit stress or less.

An example of a method for producing the (power generation unit 40) piezoelectric element of this embodiment will be specifically described below.
(1) In the case of a piezoelectric element having a unimorph structure (First step) A resin and a solvent and, if necessary, an additive such as a plasticizer are added to a piezoelectric ceramic powder material, and stirred and dispersed to obtain a paste.
(Second step) A film is formed to a thickness of 100 μm or less by a doctor blade, gravure printing, screen printing or the like, and dried.
(Third step) After the film body is cut to a required size, a binder and a firing treatment are performed in a firing furnace to obtain a fired body of the sheet-like piezoelectric body 42.
(Fourth step) An extremely thin adhesive is applied to the metal electrode plate (vibrating body 20), and the fired body (piezoelectric body 42) is bonded by pressure bonding.
(Fifth Step) A conductive adhesive is thinly applied to the exposed surface of the fired body (piezoelectric body 42) and cured and bonded at a required temperature to obtain the electrode film 44. The electrode film 44 may be formed by a metal vapor deposition method or a sputtering method.
Then, an electric field of 3 KV / mm or less is applied between the electrode film 44 and the vibrating body 20 to perform polarization treatment, and the piezoelectric body 42 is polarized as shown in each drawing of FIG.
(Sixth Step) A spiral as shown in FIG. 2A is obtained by processing the vibrating body 20 by laminating the piezoelectric body 42 and the electrode film 44 by a laser processing method, a punching method, an NC processing method, or the like. A piezoelectric element having a shape is obtained.

  The piezoelectric element created by the above method is fixedly mounted on the insulating base 32 of the housing 30 and then the vibrating body 20 and the electrode film 44 are connected to the external electrodes 70a and 70b by connection lines 72 to 75, respectively. .

(2) In the case of a piezoelectric element having a bimorph structure (First step) Similar to the manufacturing method of a unimorph structure, a paste of a piezoelectric ceramic powder material is prepared, and two piezoelectric ceramic sheets are formed.
(2nd process) A binder removal and a baking process are performed similarly to the manufacturing method of a unimorph structure.
(Third Step) An adhesive is applied very thinly to the metal electrode plate (vibrating body 20), and the two piezoelectric ceramic sheets are bonded and bonded together so that the vibrating body 20 is sandwiched therebetween.
(Fourth step) Similarly to the manufacturing method of the unimorph structure, a conductive adhesive is thinly applied to both sides of the exposed fired body (piezoelectric body 42), and cured and bonded at a necessary temperature, whereby the electrode film 44 is obtained. Get. Thereafter, an electric field of 3 KV / mm or less is applied between the electrode film 44 and the vibrating body 20 to perform polarization treatment, and the piezoelectric body 42 is polarized as shown in each drawing of FIG.

The subsequent steps are the same as those in the sixth and subsequent steps of the method for manufacturing the unimorph piezoelectric element.
Note that the above steps are not necessarily performed in this order, and may be performed at the same time or in an appropriate order.
In place of the above third step, after performing a paste preparation step of preparing a conductive paste obtained by pasting a metal powder exemplified by a mixed powder of silver and palladium or an alloy powder of silver-palladium. Alternatively, the conductive paste may be applied to the piezoelectric ceramic sheet, and another piezoelectric ceramic sheet may be further bonded and pressure-bonded to each other. In this case, the above-described baking treatment as the second step may be performed after the bonding step (third step) with the conductive paste.

The operation and effect of the piezoelectric generator 10 of the present embodiment will be described.
The power generation unit 40 (piezoelectric element) of the present embodiment has a plate shape that is curved in plan view, more specifically, a spiral shape in plan view. Thereby, the path length from the base end portion 24 of the outer periphery of the spiral to the weight 50 at the center of the spiral (tip portion 25) can be increased, and the resonance frequency of the power generation unit 40 is reduced with respect to the outer dimensions of the housing 30. can do.

At this time, the shape of the vibrating body 20 in plan view is a circular spiral, and the entire body excluding the vicinity of the base end portion 24 is formed in a curved shape, so that the vibrating body 20 (vibration unit piece) to which the base end portion 24 is fixed is formed. 21 and 22) undergoes bending deformation throughout.
On the other hand, when the spiral shape of the vibrating body 20 is a square spiral, torsional deformation occurs in the straight portion corresponding to the side of the square, and the power generation efficiency decreases. Therefore, in the case of the piezoelectric generator 10 using the spiral vibrating body 20 formed of a circular spiral as the power generation unit 40 as in the present embodiment, it is possible to realize high power generation efficiency as well as downsizing.
Further, as shown in FIG. 2A, the vibrating element pieces 21 and 22 each having a spiral band shape are fitted to each other with no gap therebetween. For this reason, the vibrating body 20 having a relatively large area can be accommodated in the downsized housing 30.

<Second embodiment>
FIG. 5 is a plan view of the piezoelectric generator 10 of the present embodiment.
In the piezoelectric generator 10 of the present embodiment, the casing 30 has a rectangular shape in plan view, the vibrating body 20 includes four vibrating element pieces 21 (21a to 21d), and the base end portion 24 of the vibrating element piece 21. Are fixed to the four corners (base 32) of the housing 30, respectively.

The housing 30 of this embodiment is provided with bases 32 at the four corners of a rectangular inner bottom surface 31. Each base 32 has a uniform upper end surface.
Each of the four vibrating element pieces 21 a to 21 d has a spiral shape, a base end is fixed to the base 32, and a tip end is gathered at the center of the housing 30. The vibrating element pieces 21a to 21d are fixed to the weights 50 at the tips thereof. The tips of the vibrating element pieces 21 a to 21 d are fixed at positions shifted by 90 degrees around the weight 50.
The vibrating element pieces 21a to 21d are fitted to each other without a gap, and constitute a vibrating body 20 having a substantially circular shape in plan view as a whole.
More specifically, the vibration element pieces 21 a to 21 d of the present embodiment are spirals of equal intervals, which are integrally formed in a spiral shape of four muscles centered on the weight 50.

The power generation unit 40 (piezoelectric element) of the present embodiment is configured by laminating a piezoelectric body 42 and an electrode film 44 (see FIG. 3) on at least one of the main surfaces of the vibrating element pieces 21a to 21d.
Hereinafter, for the sake of simplicity, the power generation unit 40 of the present embodiment exemplifies a unimorph type in which the piezoelectric body 42 and the electrode film 44 are stacked only on the upper surfaces of the vibrating element pieces 21a to 21d.

Four connection lines 72a, 72b, 73a, and 73b are connected to the external electrode 70a, and are connected to the electrode film 44 on the upper surface in the vicinity of the base end portion 24 of each of the vibration element pieces 21a to 21d. Yes.
Four connection lines 74a, 74b, 75a, and 75b are connected to the external electrode 70b, and are connected to the lower surface in the vicinity of the base end portion 24 of the vibration element pieces 21a to 21d, respectively. Metal electrodes (vibrating body 20) are exposed on the lower surfaces of the vibrating element pieces 21a to 21d.
That is, the external electrode 70 a has the same potential as the electrode film 44, and the external electrode 70 b has the same potential as the vibrating body 20.
Accordingly, the alternating current generated between the electrode film 44 and the vibrating body 20 due to the reciprocating swing of the vibrating body 20 is taken out from the external electrodes 70a and 70b.

  The standing wall surface 33 of the housing 30 has a through hole for guiding one or more of the connection lines 72 a to 75 b from the hollow interior of the housing 30 to the external electrode 70. In other words, the connection lines 72 a to 75 b are wound around from the vicinity of the base end portion 24 of the power generation unit 40 to the external electrode 70 through the inside of the standing wall surface 33 of the housing 30.

  In the piezoelectric generator 10 of the present embodiment, three or more vibrating bodies 20, specifically, four narrow strip-like vibrating element pieces 21 a to 21 d are configured, and each vibrating element piece 21 a to 21 d is formed in a housing 30. The inner bottom surface 31 is fixed to each corner. Accordingly, the bending rigidity of the vibration element pieces 21a to 21d in the perpendicular direction is sufficiently reduced so that the resonance frequency of the power generation unit 40 is 10 Hz or less as seen in vibration during walking or running, while the vibration body 20 The displacement in the plane direction is stably suppressed.

<Third embodiment>
FIG. 6 is a perspective view showing an example of the piezoelectric generator 10 of the present embodiment.
FIG. 7A is a plan view of the piezoelectric generator 10 of the present embodiment, FIG. 7B is a cross-sectional view taken along the line BB in FIG. 7A, and FIG. It is CC sectional drawing. Note that, in the cross-sectional view taken along the line BB in FIG. 4B, the front half of the spiral vibrating body 20 on the paper surface is illustrated by a virtual line.

In the piezoelectric generator 10 of the present embodiment, the casing 30 and the casing lid 60 are elongated, and two pairs of external electrodes 70 and 71 are provided on the outer side surface 30 a facing the casing 30. Thus, it is different from the piezoelectric generator 10 of the first embodiment shown in FIGS.
Hereinafter, regarding the piezoelectric generator 10, the left-right direction in FIG. 7A is the longitudinal direction, the up-down direction in FIG. 7B is the width direction, and the up-down direction in FIG.

  The power generation unit 40 according to the present embodiment is sandwiched between the vibrating body 20 in which the distal end portion 25 swings reciprocally with respect to the housing 30, the base end portion 24 of the vibrating body 20, and the housing 30, and swings the vibrating body 20. And a piezoelectric body 42 (42a to 42d) that generates power by receiving stress generated by the movement. And the vibrating body 20 of this embodiment has both flexibility with respect to multiple directions (width direction and thickness direction) orthogonal to the extending direction (longitudinal direction of the piezoelectric generator 10), and The resonance frequencies of the power generation unit 40 in the plurality of directions are both 10 Hz or less.

The vibrating body 20 of the present embodiment is a spiral spring that has further flexibility in the extending direction (longitudinal direction) of the vibrating body 20.
The material of the vibrating body 20 is not particularly limited, and the presence or absence of conductivity is also arbitrary. Specifically, in addition to a metal material, a plastic or a ceramic material may be used.

That is, the vibrating body 20 of the present embodiment has flexibility in at least the extending direction of the vibrating body 20 and the direction orthogonal thereto. The piezoelectric body 42 is provided between the base end portion 24 of the vibrating body 20 and the housing 30.
In addition, since the vibrating body 20 is a spiral spring, the resonance frequency in the width direction and the thickness direction can be easily reduced to 10 Hz or less.

In the vibrating body 20 of the present embodiment, the distal end side is spirally wound, a weight 50 is provided at the distal end portion 25, and a linear rod-shaped shaft portion is formed at the proximal end portion 24.
The winding axis direction of the spiral spring is the longitudinal direction of the piezoelectric generator 10. The shaft portion of the base end portion 24 extends integrally on the winding shaft from the base end of the spiral spring.
The base end portion 24 of the vibrating body 20 is fixed to the inner wall surface of the box-shaped housing 30 by four types of piezoelectric bodies 42a to 42d.
The piezoelectric bodies 42a to 42d have an upper end that is narrower than the width of the fixed end (lower end), and the upper end supports the base end portion 24 of the vibrating body 20 without interfering with each other.

  As will be described later with reference to FIG. 9, the piezoelectric body 42 of the present embodiment is configured by alternately stacking one or more metal inner layer electrodes 441 and 442 and a plurality of piezoelectric layers 421 made of a piezoelectric material. It has a laminated structure. In addition, as shown in each drawing of FIG. 3, the piezoelectric body 42 has a bulk structure piezoelectric material in which electrode films (not shown in the present embodiment) are attached to the positive electrode side and the negative electrode side of the polarized piezoelectric material, respectively. A power generator may be used.

A plurality of piezoelectric bodies 42 a to 42 d arranged in the extending direction of the vibrating body 20 are sandwiched between the base end portion 24 of the vibrating body 20 and the housing 30. The piezoelectric generator 10 further includes external electrodes 70a, 70b, 71a, and 71b that are exposed outside the housing 30 and are electrically connected to the plurality of piezoelectric bodies 42a to 42d.
In the present embodiment, the piezoelectric bodies 42a to 42d and the external electrodes 70a, 70b, 71a, 71b are arranged in such a direction that the electromotive forces generated by the piezoelectric bodies 42a to 42d are added to each other by the swinging of the vibrating body 20. Are connected.

Specifically, as shown in FIGS. 7A and 7C, the piezoelectric body 42a and the piezoelectric body 42b are shifted from each other in the longitudinal direction on the standing wall surfaces 33a and 33b that face each other and extend in the longitudinal direction. Standing at the position. That is, in the present embodiment, the plurality of piezoelectric bodies 42 being arranged in the extending direction of the vibrating body 20 means that the plurality of piezoelectric bodies 42 are provided at different positions with respect to the extending direction. Say. Therefore, in addition to the case where the plurality of piezoelectric bodies 42 are aligned in the extending direction, the piezoelectric bodies 42 extend at positions shifted from each other in the width direction or the thickness direction of the piezoelectric generator 10 as in the piezoelectric bodies 42a and 42b. Including the case where they are lined up in the direction.
The piezoelectric body 42a and the piezoelectric body 42b are disposed at positions shifted from each other in the longitudinal direction with their tip portions facing each other inward. The proximal end portion 24 of the vibrating body 20 is restricted from translational movement in the width direction and rotational movement in the translational direction (rotation around the thickness direction axis) by both distal ends of the piezoelectric body 42a and the piezoelectric body 42b. Yes.

On the other hand, as shown in FIGS. 4A and 4B, the piezoelectric body 42c and the piezoelectric body 42d are both erected on the inner bottom surface 31 at positions shifted from each other in the longitudinal direction.
The piezoelectric body 42c and the piezoelectric body 42d are both fixed to the inner bottom surface 31 with the tip portion facing upward. Then, the translational movement in the thickness direction and the rotation in the thickness direction (rotation around the width direction) are restricted by the distal ends of the piezoelectric body 42c and the piezoelectric body 42d. Yes.
Hereinafter, the standing direction from the installation surface of the piezoelectric bodies 42a to 42d is referred to as the height direction of the piezoelectric body.
Further, the translational movement in the longitudinal direction of the base end portion 24 of the vibrating body 20 is restricted by the piezoelectric bodies 42a to 42d.

As described above, the vibrating body 20 is in a cantilever state with the piezoelectric body 42 as a fixed end.
That is, the power generation unit 40 of the present embodiment includes the vibrating body 20 having the piezoelectric body 42 as a fixed end and cantilevered by the piezoelectric body 42, and the weight 50 provided at the tip thereof.

  The piezoelectric generator 10 of the present embodiment separates the piezoelectric body 42 having a high resonance frequency due to high hardness and the flexible rocking portion of the vibrating body 20, and causes the vibrating body 20 to vibrate at a low resonance frequency of 10 Hz or less. It is something to be made. In the piezoelectric generator 10 of the present embodiment, a load generated at the base end portion 24 that is a holding point of the vibrating body 20 is periodically applied to the piezoelectric body 42. That is, the piezoelectric generator 10 of the present embodiment does not resonate the piezoelectric body 42 itself, but applies a load obtained by resonating another member at a low frequency to the piezoelectric body 42, and the alternating current is generated by the piezoelectric effect. Is what you get.

When an acceleration load in an arbitrary direction is applied to the casing 30, the weight 50 vibrates relative to the casing 30 by the inertial force of the weight 50.
Here, the piezoelectric generator 10 of the present embodiment is influenced by the piezoelectric body 42 having a high material hardness because the piezoelectric body 42 is disposed on the housing 30 side of the base end portion 24 of the vibrating body 20. The resonance frequency can be adjusted by the physical characteristics of the vibrating body 20 and the weight 50 without any problems.
The bending rigidity of the vibrating body 20 and the weight of the weight 50 are adjusted so that the resonance frequency of the vibrating body 20 is 10 Hz or less in all of the longitudinal direction, the width direction, and the thickness direction. Thereby, the piezoelectric generator 10 applies the periodic vibration of 10 Hz or less during walking or running, which substantially matches the resonance frequency of the vibrating body 20, to the housing 30, so that the weight 50 and the vibrating body 20 are unique. The piezoelectric body 42 is vibrated, and the restraint point reaction force is applied to the piezoelectric body 42 to cause distortion.

More specifically, when the weight 50 is reciprocally swung in the width direction, the piezoelectric body 42a and the piezoelectric body 42b are repeatedly compressed or pulled together. That is, when the weight 50 moves upward in FIG. 7A, the piezoelectric bodies 42a and 42b are both subjected to compressive stress. When the weight 50 moves downward in the figure, the piezoelectric bodies 42a and 42b are both subjected to tensile stress.
Further, when the weight 50 reciprocally swings in the thickness direction, the piezoelectric body 42c and the piezoelectric body 42d repeat the compression state or the tension state by reversing each other. That is, when the weight 50 moves upward in FIG. 7B, the piezoelectric body 42c receives compressive stress, while the piezoelectric body 42b receives tensile stress. Further, when the weight 50 moves downward in the figure, the piezoelectric body 42a receives tensile stress and the piezoelectric body 42b receives compressive stress.

FIG. 8 is an enlarged view of FIG. 7A regarding the vicinity of the piezoelectric body 42. However, illustration of the vibrating body 20 is omitted for explanation.
The piezoelectric body 42a and the piezoelectric body 42b are respectively provided inward in the width direction (vertical direction in FIG. 8) from the opposing standing wall 33, and the piezoelectric body 42c and the piezoelectric body 42d are both thick from the inner bottom surface 31. It is erected in the direction (above the plane of FIG. 8).

FIG. 9A is a cross-sectional view of the piezoelectric body 42 cut in the standing direction (height direction). The piezoelectric body 42 has a laminated structure in which a plurality of piezoelectric layers 421 made of a piezoelectric material and inner layer electrodes 441 and 442 are alternately laminated. An electrode film 44 is deposited on the upper surface of the uppermost piezoelectric layer 421a and the lower surface of the lowermost piezoelectric layer 421b.
The piezoelectric layers 421 of this embodiment are each polarized in the thickness direction. The arrow from the plus side to the minus side of the polarization is shown in the figure.
Of the plurality of stacked piezoelectric layers 421, the surfaces corresponding to the positive direction of the polarization direction are electrically connected to each other by the electrode 45. Similarly, surfaces of the piezoelectric layer 421 corresponding to the negative direction of the polarization direction are electrically connected to each other by the electrode 46.
More specifically, the polarization directions of the stacked piezoelectric layers 421 are alternately reversed, and the upper surfaces of the odd-numbered piezoelectric layers 421 and the lower surfaces of the even-numbered piezoelectric layers 421 are connected by the electrodes 45. The lower surface of the odd-numbered piezoelectric layer 421 and the upper surface of the even-numbered piezoelectric layer 421 are connected by the electrode 46.
The electrode 45 and the electrode 46 are provided on opposite sides of the piezoelectric body 42 and are electrically insulated from each other.

FIG. 9B is a modified view when the piezoelectric body 42 is pressed in the height direction.
When the piezoelectric body 42 is pressed in the height direction and the piezoelectric layer 421 is compressed and deformed in the thickness direction as indicated by an arrow in the figure, the piezoelectric layer 421 has an electromotive force between both end surfaces (upper and lower surfaces) in the polarization direction. Occurs. Specifically, the positively polarized surface of the piezoelectric layer 421 has a positive potential, and the negatively polarized surface has a negative potential. Here, in the piezoelectric body 42 of the present embodiment, surfaces having a common polarization direction of a plurality of piezoelectric layers 421 are connected to each other by electrodes 45 and 46, and in this case, a negative potential (−output) is applied to the electrode 45. ), A positive potential (+ output) is generated at the electrode 46.
On the other hand, contrary to FIG. 9B, when the piezoelectric body 42 is extended in the height direction from the natural state of FIG. 9A (not shown), each piezoelectric layer 421 is thick in the thickness direction. Thus, a positive potential (+ output) is generated at the electrode 45 and a negative potential (−output) is generated at the electrode 46.
Then, by applying a compressive or tensile stress to each piezoelectric layer 421 periodically, alternating currents having opposite phases to each other are continuously output to the electrodes 45 and 46.

Returning to FIG. 8, in the piezoelectric generator 10 of the present embodiment, the piezoelectric body 42 a and the piezoelectric body 42 b are electrically connected so that the electrodes that become + outputs when the compression force is applied to each other have the same potential. It is connected. The piezoelectric body 42a and the piezoelectric body 42b are electrically connected so that the electrodes that are -output when the compressive force is applied to each other have the same potential.
On the other hand, the piezoelectric body 42c and the piezoelectric body 42d are an electrode which becomes + output when a compressive force is applied to the piezoelectric body 42c, and an electrode which becomes -output when a compressive force is applied to the piezoelectric body 42d. Are electrically connected. Then, an electrode that outputs − when a compressive force is applied to the piezoelectric body 42c and an electrode that outputs + when a compressive force is applied to the piezoelectric body 42d are electrically connected.

Specifically, in the piezoelectric body 42a and the piezoelectric body 42b, the electrodes 45a and 46a, which become + outputs when a compressive force is applied to each, are connected to the same potential as the external electrode 70a via the connection lines 72a and 72b. Has been. Similarly, in the piezoelectric body 42a and the piezoelectric body 42b, the electrodes 46a and 46b, which are -outputs when a compressive force is applied thereto, are connected to the same potential as the external electrode 71a via the connection lines 73a and 73b. Yes.
On the other hand, an electrode 45c that becomes + output when a compressive force is applied to the piezoelectric body 42c and an electrode 45d that becomes -output when a compressive force is applied to the piezoelectric body 42d are connected via connection lines 72c and 72d. It is connected to the same potential as the external electrode 70b. Then, an electrode 46c that becomes -output when a compressive force is applied to the piezoelectric body 42c and an electrode 46d that becomes + output when a compressive force is applied to the piezoelectric body 42d are connected via connection lines 73c and 73d. The external electrode 71b is connected to the same potential.

  When the weight 50 swings in the width direction, the piezoelectric bodies 42a and 42b are simultaneously compressed or pulled in the height direction to produce a piezoelectric effect. Therefore, the generated currents are added and an alternating current is extracted from the external electrode 70a and the external electrode 71a.

  Further, when the weight 50 swings in the thickness direction, the piezoelectric bodies 42c and 42d are compressed or pulled in the opposite direction in the height direction, and a piezoelectric effect is generated. Therefore, the generated currents are added and an alternating current is extracted from the external electrode 70b and the external electrode 71b.

  The alternating current output between the external electrodes 70a and 71a based on the acceleration in the width direction and the alternating current output between the external electrodes 70b and 71b based on the acceleration in the thickness direction are mutually The phases may not match. For this reason, the output currents are preferably rectified by diodes (not shown) and then joined together.

The vibrating body 20 of the present embodiment is a spiral spring and has a resonance frequency that is substantially equal not only in the width direction and thickness direction of the piezoelectric generator 10 but also in all directions of 360 degrees around the longitudinal axis.
Further, as described above, the piezoelectric bodies 42a and 42b and the piezoelectric bodies 42c and 42d are connected to the external electrodes 70a, 70b, 71a, 71b by adding the alternating currents generated in the piezoelectric bodies 42a-73d through the connection lines 72a-73d. Yes.
Therefore, according to the piezoelectric generator 10 of the present embodiment, the external electrode 70a can be used regardless of the direction of vibration of the vibrating body 20, that is, the direction of the acceleration load applied to the housing 30 is 360 degrees around the longitudinal axis. , 70b, 71a, 71b, an alternating current can be taken out.

<Fourth embodiment>
FIG. 10A is a plan view of the piezoelectric generator 10 of the present embodiment, and FIG. 10B is a cross-sectional view taken along the line BB. In FIG. 5A, the housing lid 60 is not shown.

  The piezoelectric generator 10 of this embodiment includes a plurality of piezoelectric bodies 42 a and 42 b arranged in the extending direction of the vibrating body 20 between the base end portion 24 of the vibrating body 20 and the housing 30. The piezoelectric bodies 42a, 42b and the external electrodes 70a, 70b are electrically connected in such a direction that the electromotive forces generated by the piezoelectric bodies 42a, 42b are added to each other by the oscillation of the vibrating body 20. Common to the three embodiments.

The vibrating body 20 of the present embodiment is a flat rectangular plate (strip shape) in plan view, and a weight 50 is attached to the distal end portion 25.
Piezoelectric bodies 42 a and 42 b are sandwiched between the base end portion 24 of the vibrating body 20 and the inner bottom surface 31 of the housing 30.
Each of the piezoelectric bodies 42a and 42b has a block shape, and a lower end surface is fixed to the inner bottom surface 31, and an upper end surface is fixed to the vibrating body 20.
The piezoelectric bodies 42a and 42b are arranged in the longitudinal direction.

  In the piezoelectric generator 10 of the present embodiment, the piezoelectric bodies 42a and 42b fixed to the housing 30, the vibrating body 20 in which the base end portion 24 is supported by the piezoelectric bodies 42a and 42b, and the distal end portion of the vibrating body 20 The power generation unit 40 is composed of the weight 50 provided in the shaft 25.

The connection line 72a electrically connects the negative electrode side of the piezoelectric body 42a and the positive electrode side of the piezoelectric body 42b. The connection line 72b electrically connects the positive electrode side of the piezoelectric body 42a and the negative electrode side of the piezoelectric body 42b.
The connection line 73a electrically connects the positive electrode side of the piezoelectric body 42b and the external electrode 70a. Therefore, the negative electrode side of the piezoelectric body 42a, the positive electrode side of the piezoelectric body 42b, and the external electrode 70a are at the same potential.
On the other hand, the connection line 73b electrically connects the negative electrode side of the piezoelectric body 42b and the external electrode 70b. Therefore, the positive electrode side of the piezoelectric body 42a, the negative electrode side of the piezoelectric body 42b, and the external electrode 70b are at the same potential.

In the primary natural vibration of the power generation unit 40, the weight 50 swings in the thickness direction. The bending rigidity of the vibrating body 20 and the mass of the weight 50 are adjusted so that the primary natural frequency is 10 Hz.
When a periodic acceleration load is applied to the housing 30 in the thickness direction and the weight 50 vibrates relative to the housing 30, the piezoelectric bodies 42 a and 42 b are subjected to compressive stress and tension according to the reciprocating vibration of the weight 50. Stress is generated in the opposite direction and alternately reversed.
The piezoelectric bodies 42a and 42b of the present embodiment have a laminated structure shown in FIG. Then, as described above, the connection line 72b is connected to the electrode 45a that becomes + output when a compressive force is applied to the piezoelectric body 42a and the electrode 46b that becomes -output when a compressive force is applied to the piezoelectric body 42b. Are electrically connected. The piezoelectric bodies 42a and 42b are connected to an electrode 46a that is output when a compressive force is applied to the piezoelectric body 42a and an electrode 46b that is output when a compressive force is applied to the piezoelectric body 42b. They are electrically connected by a line 72a.
Therefore, when the weight 50 swings in the thickness direction and an alternating current is generated in the piezoelectric bodies 42a and 42b, the currents are added to each other through the connection lines 72a, 72b, 73a, and 73b and output to the external electrodes 70a and 70b. .

  Instead of the piezoelectric generator 10 of the present embodiment, alternating currents from the positive or negative electrodes of the piezoelectric bodies 42a and 42b may be independently output to the four external electrodes. In this case, the alternating currents output to the four external electrodes may be combined and output in the addition direction, or may be combined after being rectified by a diode (not shown) and output. Good.

<Fifth embodiment>
FIG. 11A is a plan view of the piezoelectric generator 10 of the fifth embodiment, FIG. 11B is a sectional view taken along the line BB, and FIG. 11C is a cross-sectional view taken along the line C- of FIG. It is C sectional drawing.

  In the piezoelectric generator 10 of the present embodiment, the vibrating body 20 is a rod-shaped body, and is fourth in that it has resonance frequencies equal to a plurality of directions (width direction and thickness direction) orthogonal to the extending direction. It is different from the embodiment.

In the present embodiment, the piezoelectric body 42 a is fixed to one of the standing wall surfaces (standing wall surface 33 a) facing the width direction of the housing 30, and the piezoelectric body 42 b is fixed to the inner bottom surface 31 of the housing 30.
The piezoelectric body 42a supports the base end portion 24 of the vibrating body 20 in the width direction from the standing wall 33a, and the piezoelectric body 42b supports the base end portion 24 of the vibrating body 20 in the thickness direction from the inner bottom surface 31.

A recess 35 for fitting the most proximal end 26 of the proximal end 24 of the vibrating body 20 is provided on the vertical wall 33c on the proximal end of the housing 30 (left side in FIGS. 11A and 11B). It has been.
The vibrating body 20 is in a cantilever state in which the most proximal end 26 of the proximal end portion 24 is fitted and fixed to the recess 35 and supported by the piezoelectric bodies 42a and 42b.
A weight 50 is attached to the distal end portion 25 of the vibrating body 20.

The vibrating body 20 of the present embodiment has a square cross section (hereinafter referred to as a cross section) with respect to the extending direction (longitudinal direction of the piezoelectric generator 10). In addition, the four sides of the cross section of the vibrating body 20 coincide with the width direction and the thickness direction of the piezoelectric generator 10, respectively.
Further, the vibrating body 20 is made of an isotropic material in the cross section. Specifically, a metal square bar or an extruded plastic material can be exemplified.
Further, the weight 50 of the present embodiment has a square cross section, and the inertia moments in the width direction and the thickness direction are equal to each other.

  Thereby, the vibrating body 20 of the present embodiment has both flexibility in a plurality of directions (width direction and thickness direction) orthogonal to the extending direction (longitudinal direction of the piezoelectric generator 10). In addition, the resonance frequencies in the plurality of directions of the power generation unit 40 are both 10 Hz or less.

When the weight 50 vibrates in the width direction of the piezoelectric generator 10, the vibrating body 20 having the most proximal end 26 fixed to the standing wall surface 33c exerts a compressive or tensile stress in the thickness direction from the proximal end portion 24 to the piezoelectric body 42a. Give periodically.
The piezoelectric bodies 42a and 42b of the present embodiment have a laminated structure shown in FIG. Between the electrodes 45a and 46a provided on both sides in the longitudinal direction of the piezoelectric body 42a, the piezoelectric body 42a receives a periodic stress in the width direction from the base end portion 24 of the vibrating body 20, thereby alternating current. Occurs.

The electrode 46a and the external electrode 71a are electrically connected by a connection line 73a. The electrode 45a and the external electrode 70a are electrically connected by a connection line 72a.
As a result, when the weight 50 reciprocally swings in the width direction with respect to the housing 30, an alternating current having an inverted potential is output to the external electrodes 70a and 71a.
In FIG. 11C, connection lines are not shown.

On the other hand, when the weight 50 vibrates in the thickness direction of the piezoelectric generator 10, compressive or tensile stress in the thickness direction is periodically applied from the base end portion 24 to the piezoelectric body 42b.
Between the electrodes 45b and 46b provided on both sides in the longitudinal direction of the piezoelectric body 42b, an alternating current is generated when the piezoelectric body 42b receives periodic stress in the thickness direction from the base end portion 24 of the vibrating body 20. .
The electrode 46b and the external electrode 71b are electrically connected by a connection line 73b. The electrode 45b and the external electrode 70b are electrically connected by a connection line 72b.
As a result, when the weight 50 reciprocally swings in the thickness direction with respect to the housing 30, an alternating current having an inverted potential is output to the external electrodes 70b and 71b.

  The alternating current output between the external electrodes 70a and 71a based on the acceleration in the width direction and the alternating current output between the external electrodes 70b and 71b based on the acceleration in the thickness direction are mutually in phase. It may not match. For this reason, the output currents may be joined together after being rectified by a diode (not shown).

In the piezoelectric generator 10 of this embodiment, the cross section of the vibrating body 20 may be circular.
Further, the weight 50 is also preferably circular in cross section, such as cylindrical or spherical.
As a result, the vibrating body 20 has a resonance frequency substantially equal in all directions of 360 degrees around the longitudinal axis.
In addition, according to the piezoelectric generator 10 of the present embodiment, the external electrode 70a regardless of the direction of vibration of the vibrating body 20, that is, the direction of acceleration load applied to the housing 30, is 360 degrees around the longitudinal axis. , 70b, 71a, 71b, an alternating current can be taken out.

  Hereinafter, the piezoelectric generator of the present invention will be described more specifically with reference to examples. In addition, this invention is not limited to a following example.

(Examples 1 and 2)
The piezoelectric generators according to the first and second embodiments described in FIGS. 2 and 5 were produced as Examples 1 and 2, respectively. Hereinafter, the symbol of the element name in a present Example respond | corresponds to the thing as described in the said embodiment or drawing.
The casing 30 of Examples 1 and 2 was in a square shape in plan view with an outer side length of 20 mm.

In the two spiral vibrators 20 (vibrating element pieces 21 and 22) of Example 1, the width dimension was 1 mm, and the spiral path length from the base end portion 24 to the tip end portion 25 was 64 mm.
The four spiral vibrators 20 (vibrating element pieces 21a to 21d) of Example 2 had a width dimension of 0.5 mm and a spiral path length from the base end part 24 to the tip part 25 of 35 mm.

  The laminated thickness dimension of the band-shaped piezoelectric element in which the vibrating body 20, the piezoelectric body 42, and the electrode film 44 are laminated is 0.1 mm in both Examples 1 and 2.

In the piezoelectric generator 10 of Example 1, a 0.07 g weight 50 made of iron was attached to the distal end portion 25 of the vibrating element pieces 21 and 22.
In the piezoelectric generator 10 of Example 2, a 0.125 g weight 50 made of iron was attached to the distal end portion 25 of the vibration element pieces 21a to 21d.

(Comparative Example 1)
FIG. 12 is a plan view of the piezoelectric generator 100 of the first comparative example. However, the external electrodes and connection lines are not shown.
In the piezoelectric generator 100 of Comparative Example 1, the vibrating body 20 supported in a cantilevered manner on the base 32 made of a non-insulating material has a linear plate shape in plan view. The dimensions of the vibrating body 20 were set to be a size that can be accommodated in the case 30 that is the same as in the first and second embodiments, the width dimension was 3 mm, and the length dimension was 15 mm. The thickness dimension was set to 0.1 mm, which is the same as in Examples 1 and 2.
In addition, the material of the vibrating body 20 of Comparative Example 1 and the materials and dimensions of the piezoelectric body 42 and the electrode film 44 on the upper surface thereof were the same as those in Examples 1 and 2.
Further, the mass of the weight 50 attached to the tip of the vibrating body 20 of Comparative Example 1 was set to 0.125 g as in Example 2.

In Examples 1 and 2 and Comparative Example 1, the elastic modulus of the vibrating body 20, the piezoelectric body 42, and the electrode film 44 was appropriately set, and the resonance frequency (primary natural frequency) of the vibrating body 20 was obtained by numerical simulation.
As a result, the resonance frequency of Example 1 was 5.4 Hz and the resonance frequency of Example 2 was 7.2 Hz, both being 10 Hz or less, whereas the resonance frequency of Comparative Example 1 was 62 Hz. Greatly exceeded.
Thus, as in the first and second embodiments, the vibrating body 20 is formed into a plurality of spiral vibrating element pieces, so that the resonance frequency of the power generation unit 40 is reduced when walking in the small piezoelectric generator 10 of 20 mm square. It was found that the frequency can be reduced to 10 Hz or less as seen during traveling. On the other hand, when a rectangular plate-like vibrating body is used as in a conventional generator, it is extremely difficult to realize a resonance frequency of 10 Hz or less in the power generation unit 40 accommodated in the casing 30 having an equivalent size. It turned out to be difficult.

(Examples 3 to 5)
Piezoelectric generators 10 according to the third, fourth and fifth embodiments shown in FIGS. 7, 10 and 11 were produced as Examples 3 to 5, respectively.
For the vibrating body 20, a polycarbonate (PC) resin having a flexural modulus of 0.23 GPa was used.

In the vibrating body 20 of Example 3 shown in FIG. 7, a cylindrical PC resin rod having a diameter of 0.3 mm and a length of 45 mm is spirally wound into 6 turns with a winding diameter of 4 mm and a pitch of 2 mm to produce a spiral spring portion. Subsequently, the base end portion 24 having a length of 5 mm is linearly extended. An iron 0.585 g weight 50 was attached to the tip portion 25 of the vibrating body 20.
The housing 30 of Example 3 was a rectangular parallelepiped having a length of 20 mm, a width of 8 mm, and a thickness of 8 mm.

The vibrating body 20 of Example 4 shown in FIG. 10 was formed into a strip shape having a width dimension of 1 mm, a thickness of 0.1 mm, and a length dimension of 13 mm. An iron 0.07 g weight 50 was attached to the tip 25 of the vibrating body 20.
The casing 30 of Example 4 was a rectangular parallelepiped having a length of 20 mm, a width of 5 mm, and a thickness of 3 mm.

The vibrating body 20 of Example 5 shown in FIG. 11 was a square bar with a square cross section having a width dimension and a thickness dimension of 0.3 mm and a length dimension of 14 mm. An iron 0.585 g weight 50 was attached to the tip portion 25 of the vibrating body 20.
The casing 30 of Example 5 was a rectangular parallelepiped having a length of 20 mm, a width of 8 mm, and a thickness of 8 mm.

(Comparative Example 2)
FIG. 13A is a plan view of the piezoelectric generator 100 of Comparative Example 2, and FIG. 13B is a sectional view taken along the line BB.
The piezoelectric generator 100 of Comparative Example 2 is obtained by attaching a plate-like piezoelectric body 42 to the main surface of the vibrating body 20 with respect to the piezoelectric generator 10 of Example 4. The electrode film provided on the surface of the piezoelectric body 42 is not shown. This aspect corresponds to the conventional generator described in Patent Document 1.
The elastic modulus of the piezoelectric element (vibrating body 20 and piezoelectric body 42) of Comparative Example 2 was 90 GPa, the width dimension was 1 mm, the thickness dimension was 0.2 mm, and the length dimension was 14 mm.
Further, an iron 0.07 g weight 50 was attached to the tip 25 of the vibrating body 20 of Comparative Example 2.
Further, in the piezoelectric element of Comparative Example 2, the base end portion 24 was fitted into the housing 30, and the base 32 was fixed to the lower surface of the vibrating body 20.
The casing 30 of Comparative Example 2 was a rectangular parallelepiped having a length of 20 mm, a width of 5 mm, and a thickness of 5 mm.

For Examples 3 to 5 and Comparative Example 2, the resonance frequency (primary natural frequency) of the vibrating body 20 was obtained by numerical simulation.
As a result, the resonance frequency of Example 3 was 8.51 Hz, the resonance frequency of Example 2 was 9.7 Hz, and the resonance frequency of Example 3 was 8.57 Hz, both being 10 Hz or less, The resonance frequency of Comparative Example 2 was 156 Hz, significantly exceeding 10 Hz.
Thus, as in the third to fifth embodiments, the swinging portion of the vibrating body 20 is separated from the piezoelectric body 42, and the piezoelectric body 42 is provided between the base end portion 24 of the vibrating body 20 and the housing 30. Thus, it has been found that the resonance frequency of the power generation unit 40 can be easily reduced to 10 Hz or less without being affected by the material hardness of the piezoelectric body 42.

  In the piezoelectric generator of the present invention, the source of the external force is not particularly limited as long as the vibrating body is swung to cause distortion in the piezoelectric body. In each of the above embodiments, vibrations during walking of humans and animals and traveling vibrations of automobiles, bicycles and the like are exemplified, but the present invention is not limited to this.

The above embodiments and examples include the following technical ideas.
(1) A housing and a piezoelectric power generation unit that is fixed to the housing and generates power by stress generated by reciprocal swinging with respect to the housing, and
A piezoelectric generator having a resonance frequency of 10 Hz or less;
(2) The power generation unit includes a vibrating body having a base end fixed to the housing, and a piezoelectric body that is joined to at least one main surface of the vibrating body and swings together with the vibrating body. Including and
The piezoelectric generator according to (1), wherein the vibrating body has a curved plate shape;
(3) The stress generated by the vibration of the power generation unit is sandwiched between the vibrating body whose front end reciprocally swings with respect to the casing, and the base end of the vibrating body and the casing. And a piezoelectric body that generates electric power upon receiving,
The vibrating body is flexible in a plurality of directions perpendicular to the extending direction of the vibrating body, and resonance frequencies in the plurality of directions of the power generation unit are both 10 Hz or less. The piezoelectric generator according to (1) above, characterized in that;
(4) The piezoelectric generator according to (2), wherein the vibrating body has a spiral plate shape;
(5) The vibrating body includes a plurality of vibrating element pieces each having a spiral plate shape, and the piezoelectric body bonded to at least one main surface of the vibrating element pieces, and
The piezoelectric generator according to (2) above, wherein the plurality of vibrating elements each have a base end fixed to the housing and a common weight attached to the tip.
(6) The casing is rectangular,
The piezoelectric generator according to (5), wherein the vibrating body includes the four vibrating elements, and the base ends of the vibrating elements are fixed to four corners of the casing, respectively.
(7) The piezoelectric generator according to (1), wherein the piezoelectric body is provided between the base end portion of the vibrating body and the housing;
(8) The piezoelectric generator according to (3), wherein the vibrating body is a helical spring that is further flexible in the extending direction of the vibrating body;
(9) The piezoelectric generator according to (3), wherein the vibrating body is a rod-like body and has resonance frequencies equal to a plurality of directions orthogonal to the extending direction of the vibrating body;
(10) A plurality of the piezoelectric bodies arranged in the extending direction are sandwiched between the base end portion of the vibrating body and the housing,
An external electrode provided exposed outside the housing and electrically connected to the plurality of piezoelectric bodies; and
(3), wherein the plurality of piezoelectric bodies and the external electrode are connected in a direction in which electromotive forces generated by the plurality of piezoelectric bodies are added to each other by swinging the vibrating body. The piezoelectric generator according to (8) or (9).

DESCRIPTION OF SYMBOLS 10 Piezoelectric generator 20 Vibrating body 21 and 22 Vibrating element piece 24 Base end part 25 Front end part 26 The most proximal end 30 Housing | casing 30a, 30b Outer side surface 31 Inner bottom face 32 Base 33 Standing wall surface 34 Groove part 35 Recessed part 36, 62 Displacement stopper 40 Power generation unit 42 Piezoelectric body 421 Piezoelectric layer 44 Electrode films 441 and 442 Inner layer electrodes 45 and 46 Electrode 50 Weight 60 Housing lid 70 and 71 External electrodes 72 to 75 Connection line 100 Piezoelectric generator NP Neutral surface

Claims (3)

A housing and a piezoelectric power generation unit that is fixed to the housing and generates power by stress generated by reciprocal swinging with respect to the housing;
The power generation unit has a resonance frequency of 10 Hz or less,
A vibrating body having a plurality of vibrating elements that are curved strip-shaped flat plates ,
The power generation unit is joined to at least one main surface of each of the plurality of vibrating element pieces whose base end portions are fixed to the housing, and the plurality of vibrating element pieces. A piezoelectric body that swings with the piece, and
The plurality of vibrating elements are mounted with a common weight that reciprocally swings in a direction perpendicular to the main surface, and has a curved shape that curves in the plane direction of the main surface and is mutually on the same plane. A piezoelectric generator characterized by being fitted adjacently. The planar view shape of the plurality of vibrating elements viewed in the direction perpendicular to the main surface is formed in a curved shape in substantially the whole except the vicinity of the base end portion,
The piezoelectric body is bonded to at least one main surface of the plurality of vibrating element pieces,
2. The piezoelectric generator according to claim 1, wherein each of the plurality of vibrating element pieces has a base end fixed to the housing and a common weight attached to the tip end. A plurality of said vibration piece is a spiral-shaped adjacent to each other on said same plane,
The weight is disposed at the center of the spiral shape;
The front ends of the plurality of vibrating element pieces are fixed at positions shifted around the weight, and the plurality of vibrating element pieces extend in a common spiral direction around the weight. 2. The piezoelectric generator according to 2.

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