JP2008192944A - Piezoelectric generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric generator which converts even week vibration energy or relatively large mechanical energy generated by natural force or artificial force to electric energy, and is excellent in reproducibility of conversion to the electric energy. <P>SOLUTION: The piezoelectric generator comprises: a roughly rectangular or roughly sectorial piezoelectric element provided with a piezoelectric plate and a reinforcing plate, which includes the piezoelectric plate polarized in the thickness direction, arranged and stuck along the longitudinal direction or radial direction of the reinforcing plate; a holding member for movably holding one end in the longitudinal direction or radial direction of the piezoelectric element; and an elastic body abutted to the holding member. The other end in the longitudinal direction or radial direction of the piezoelectric element is fixed by a different holding member. When the elastic body is displaced by external force applied to the holding member or the elastic body and when the external force is removed and the elastic body is returned to its original shape, the electric energy is obtained by the displacement of the piezoelectric element. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a piezoelectric power generation device that converts mechanical energy such as vibration into electrical energy.

In recent years, in order to suppress global warming due to carbon dioxide or the like, a piezoelectric power generation apparatus that uses natural forces such as wind power and hydraulic power without using fossil fuels has attracted attention. For example, a wind power generator that has been put into practical use generates electric power by electromagnetic induction by rotating a propeller with wind power and rotating a motor. However, these have problems that the apparatus is large and expensive, the installation location is limited, and a predetermined area and installation interval are required.

Therefore, power generation by a piezoelectric element is attracting attention. With regard to this technology, Patent Document 1 discloses a power generation element having a piezoelectric element bent in a convex shape by a horizontal holding force from the outside, a holding member that holds the piezoelectric element so as to be bent, and an elastic body part. By applying an external force to the convex part of the piezoelectric element, the elastic body is pressed from the piezoelectric element to be contracted and bent into a concavely bent piezoelectric element, and the external force applied to the piezoelectric element Is removed, and when the elastic element returns to its original shape and the piezoelectric element bent in the concave is restored to the piezoelectric element bent in the convex, the power generation apparatus is bent to generate power, Is disclosed.

Japanese Patent No. 3768520

This power generation device has the advantage that a large electromotive force can be obtained instantaneously for mechanical energy with a certain threshold, but displacement occurs against the horizontal holding force, which causes propagation of displacement due to external force. However, there are disadvantages in that it is difficult to obtain the reproducibility of displacement with respect to a certain external force, and the reproducibility of conversion into electrical energy may not be obtained.

The present invention has been made in view of such circumstances, and can convert relatively large mechanical energy into electric energy efficiently from weak vibration energy generated by natural force or artificial force. An object of the present invention is to provide a piezoelectric power generation device with excellent reproducibility of conversion into energy.

A substantially rectangular or substantially sector-shaped piezoelectric element having a piezoelectric plate and a reinforcing plate, wherein the piezoelectric plate is arranged and stuck in the thickness direction along the longitudinal direction or radial direction of the reinforcing plate. A piezoelectric element including:
A holding member that movably holds one end in the longitudinal direction or radial direction of the piezoelectric element;
An elastic body that contacts the holding member,
The other end in the longitudinal direction or radial direction of the piezoelectric element is fixed by another holding member,
When the elastic body is displaced by an external force applied to the holding member or the elastic body, the external force is removed, and when the elastic body returns to its original shape, the piezoelectric element is displaced to obtain electric energy. A piezoelectric power generation device (Claim 1) is provided. 2. The piezoelectric power generator according to claim 1, wherein the holding member that movably holds one end in the longitudinal direction or the radial direction of the piezoelectric element has a groove portion for receiving the reinforcing plate. I will provide a.

  3. The piezoelectric element according to claim 1, further comprising a plurality of piezoelectric elements, wherein the first holding member is arranged at the center of the circle, and a plurality of piezoelectric plates having substantially the same shape are arranged radially from the center of the circle. A power generator (Claim 3), wherein electromotive forces are separately taken out from the plurality of piezoelectric elements, and the direction and magnitude of an external force are detected from position information of each piezoelectric element and a measured value of the electromotive force. A piezoelectric power generation device according to claim 3 (claim 4) is provided.

According to the piezoelectric power generation device according to the present invention, when an external force is applied to the holding portion of the piezoelectric element, when the entire piezoelectric element moves, the external force is removed, and when returning in the reverse direction by the restoring action of the elastic body, An electromotive force is generated. Since the holding portion movably supports one end of the piezoelectric element and reduces the stress in the length direction of the piezoelectric element, the stress is less likely to concentrate on the local portion of the piezoelectric element itself, and natural force or artificial force A wide range of mechanical energy can be efficiently converted into electrical energy from the weak vibration energy generated by the above to a relatively large vibration energy. In addition, the number of parts is relatively small and assembly is easy.

In addition, one end of the piezoelectric element is in a supporting state in which an external force does not act directly, and a large load is hardly applied to a part of the piezoelectric portion even when sudden displacement occurs, and the power generation portion is not damaged.

In the system of the present invention, if a power generation device is arranged in a portion where a force is generated by vibration generated in a structure, this force can be used effectively, and the operating rate and power generation efficiency are further increased. Effective use of unused energy is possible without relying on resources such as fossil fuels and nuclear power.

1, 2 and 3 are sectional views showing a schematic structure of the piezoelectric power generation apparatus 100 and displacement states of the piezoelectric elements 10 and 10 ′. FIG. 4 shows a plan sectional view (corresponding to FIG. 2) of the piezoelectric power generation apparatus 100. FIG. The piezoelectric power generation device 100 includes piezoelectric elements 10 and 10 ′ formed by bonding a rectangular piezoelectric plate 11 and a rectangular reinforcing plate 12, a holding unit 20, and an elastic body unit 30. One end of the rectangular piezoelectric elements 10 and 10 ′ is movably supported by the holding member 20. The other ends of the rectangular piezoelectric elements 10 and 10 ′ are fixed to the side frame 42. The piezoelectric element 10 and the piezoelectric element 10 ′ are positioned in the radial direction with the approximate center of the holding member 21 as the center of the approximate circle, and the diameter of the circle. Reinforcing plates 12, 12 ′ are inserted into the holding member 21 along with the displacement of the piezoelectric element, and a groove for receiving the reinforcing plate is formed. The reinforcing plate slides along the groove, and the piezoelectric element is excessively moved in the longitudinal direction. Bend without stress. The planar shape of the holding member 21 may be arbitrary, but is preferably a square, a rectangle, a polygon, or the like. The piezoelectric portion has symmetry, and the displacement also maintains symmetry with respect to an external force perpendicular to the paper surface in FIG. In the center of the holding member 21, elongated columnar extensions 22, 22 'are extended in the vertical direction of the reinforcing plate 12. The piezoelectric element / holding unit 20 is housed in a housing or frame 41, 41 ′, 42. The extension portion protrudes from a hole formed in the housing or frame 41, 41 'so that the position of the piezoelectric element is movable with respect to the housing or the frame. A button portion 23 is fixed to the extension portion 22 of the holding member so that an external force is easily applied. A helical metal spring (hereinafter referred to as a coil spring) 31 is mounted between the holding member 21 and the frame 41 ′ so as to surround the extension 22 ′, and the coil spring 31 can move the holding member by an external force from the button portion. The holding part and the piezoelectric element are restored to their original positions.

  An elastic body is brought into contact with the holding portion 21, and the elastic body portion is held or fixed by a housing or a frame. When a predetermined pressure is applied to the holding member 21, the preload mechanism and the restoring elastic body portion 30 can be used together to resist this pressure. Further, the preload and the applied load may be balanced with the restoring force of the elastic body portion 30.

The piezoelectric plate 11 has a structure in which electrode films (not shown) are formed on the front and back surfaces of a rectangular piezoelectric ceramic, and the piezoelectric ceramic of the piezoelectric plate is polarized in the thickness direction. The piezoelectric plate 11 is bonded to the reinforcing plate 12 using a resin adhesive. A piezoelectric polymer may be used instead of the piezoelectric ceramic. The shape of the piezoelectric plate is not limited to this, and may be, for example, a substantially fan-shaped or square piezoelectric ceramic plate. A piezoelectric ceramic plate and a reinforcing plate such as a metal plate or plastic (hereinafter referred to as a reinforcing plate 12) are attached. Those having a combined structure (for example, one corresponding to a needle driving unit of an electric knitting machine, a piezoelectric acoustic element of a piezoelectric speaker, or one configured as a unimorph element or a bimorph element) can be used. In the bimorph element, both the parallel type with the same polarization direction or the series type with the opposite direction can be preferably used. The material of the piezoelectric element is not particularly limited, but ceramics such as lead zirconate titanate and barium titanate can be used. It can also be used.

The reinforcing plate 12 is made of at least one of metal and resin, and is larger than the reinforcing plate 12 for mounting the piezoelectric plate 11, for example, has a long rectangular shape. In the case where a resin plate is used as the reinforcing plate 12, a metal foil is provided on the surface to be bonded to the piezoelectric plate 11 in order to facilitate removal of electrode leads (not shown) from the piezoelectric plate 11. It is preferable to use what is.

  The holding part 20 includes extension parts 22 and 22 'and a button part, and is integrated by, for example, coupling with a bolt (not shown). As shown in FIG. 1, a stopper 23 can be attached so that excessive displacement does not occur in the piezoelectric element portion. The stopper 23 may touch the frame upper part 41 when an external force is applied, and may be provided with an extension part 23 so as to contact the extension part of the holding member at the time of restoration. Further, a stopper portion (not shown) can be separately provided under the extension portion 22 '.

  The holding member 21 and its extension 22 ′ may be integrally formed of a metal, and the piezoelectric element 10 may be coupled. The extensions 22 and 22 ′ are provided as metallic elongated cylindrical members, and the mounting portion and stopper of the piezoelectric element 10 are provided. The portion 23 can be separately molded with plastic and combined with this to form the holding portion 20 as a whole.

  Further, the elastic body portion 30 is composed of a coil spring 31 and an abutting member provided at the end of the coupling portion for holding it, and is fixed to a part of the frame 41 ′, the end surface of the holding member, and the abutting member Can be omitted. The elastic body applies a repulsive force against the external force applied to the holding portion to bend the piezoelectric element.

  The casing or frame is preferably made of a material having an appropriate rigidity such as metal or plastic. In the case of metal, it can be used as a part of the wiring as a conductor, but when the contact with the electrical wiring system is disadvantageous, an insulating coating is considered.

The piezoelectric power generation apparatus 100 is installed in a state where the piezoelectric element stops at a predetermined position as shown in FIG. 1 when the holding unit 20 is not loaded, or in a state where the coil spring 31 maintains a predetermined length without load. The It is preferable to arrange the piezoelectric element 10 so that a certain preload is applied to the piezoelectric element 10 so that the piezoelectric element 10 stops in the state shown in FIG. That is, the coil spring 31 is installed so as to maintain the neutral state in which the piezoelectric element 10 is convex in the direction opposite to the external force direction.

  1, the external force acts on the holding part 20 through the extension part 22 of the holding member 21 and further acts on the coil spring 31, and the coil spring 31 is pushed down. . FIG. 2 illustrates a state where the external force is increased and acts downward to bend the piezoelectric element. When the external force further increases, it bends so as to be concave in the external force direction as shown in FIG. At this time, the button part 23 may act as a stopper. When the external force disappears or becomes upward, the coil spring 31 repels suddenly and pushes up the entire movable holding portion in the direction opposite to the external force. While the no-load state is maintained as it is, the piezoelectric element returns to the state shown in FIG. Subsequently, when an external force is periodically applied, the above change is repeated, and the piezoelectric element repeats periodic displacement. At this time, the piezoelectric plate 11 expands and contracts in the length direction at a predetermined cycle. When the piezoelectric plate 11 expands and contracts, an electromotive force is generated because the piezoelectric ceramics of the piezoelectric plate are polarized in the thickness direction. FIG. 8 shows a circuit configuration for recovering electrical energy from the piezoelectric generator 100.

  For example, when a periodic external force is applied to the holding portion 20, the piezoelectric plate 11 is periodically displaced with respect to the external force so as to be convex in the opposite direction and the forward direction. Piezoelectric plates placed on the opposite side of the piezoelectric plate have opposite directions of expansion and contraction, and if the polarization direction is parallel to the thickness direction of the reinforcing plate, the amplitude direction is completely reversed and the direction of the electromotive force is The reverse is true. FIG. 12 schematically shows an example of a power generation state when an external force and a force from an elastic body are applied to the holding unit 20. FIG. 13 shows an electromotive force generation situation. A small amplitude is seen in the generation of the electromotive force because the piezoelectric element does not smoothly follow the application of an external force and the vibration of the piezoelectric element is attenuated. The main reason is that the piezoelectric element is rigid and does not match the acceleration applied by the external force. Therefore, by controlling the material and shape of the piezoelectric element reinforcement plate and piezoelectric plate, the rigidity is weakened while maintaining elasticity, and the above-mentioned smooth generated electromotive force waveform having no small amplitude of electromotive force is obtained. Can do.

  In the bimorph type piezoelectric element in which the polarization directions of the piezoelectric plates arranged above and below the reinforcing plate are parallel, the electrode film on the bonding surface side of the piezoelectric plate opposite to the electrode film on the bonding surface side of the piezoelectric plate 11 The structure which short-circuits may be sufficient. For this reason, a metal foil / metal plate can be used as the reinforcing plate 12. On the other hand, when the polarization directions of both piezoelectric plates are opposite, the reinforcing plate 12 has a structure that does not short-circuit the electrode film on the adhesive surface side of the piezoelectric plate 11 and the electrode film on the adhesive surface side of the opposite piezoelectric plate. There is a need. Therefore, when a metal foil / metal plate is used as the reinforcing plate 12, the metal foil / metal plate is interposed via an insulating film so that one of the upper and lower piezoelectric plates is not short-circuited with the metal foil / metal plate. It is necessary to devise such as adhering to. In addition, when using a reinforcing plate 12 that is formed by attaching a metal foil to a resin substrate, such as a printed wiring board, the metal foil is connected to the inner peripheral side portion so that the piezoelectric plates arranged above and below are insulated. What is necessary is just to set it as the pattern divided | segmented into the outer peripheral side part.

Therefore, this electromotive force can be taken out by connection considering positive and negative, as illustrated in FIG. Since the electrical energy obtained in this way is AC power, it is usually converted to DC power through a rectifier circuit as shown in FIG. 9 and charged in a power storage device such as a capacitor or a secondary battery, or directly “ The load can be supplied to drive the load. Alternatively, DC power can be obtained through a rectifier circuit for each piezoelectric element or by inserting a rectifier circuit for each piezoelectric element group.

Thus, the electric energy obtained efficiently can be charged in a power storage device such as a capacitor or a secondary battery, or directly supplied to the load to drive the load. When the deformation is performed with symmetry, the plurality of piezoelectric elements need not be provided with a rectifier circuit for each piezoelectric element 13 as shown in FIG. 9, and can be rectified with a single rectifier circuit. Therefore, the circuit can be simply configured.

  Since the displacement amount of the piezoelectric element 10 can be adjusted by changing the material and thickness of the reinforcing plate and the shape and number of the piezoelectric elements, a piezoelectric power generation apparatus using a piezoelectric element that displaces even with a weak force is realized. If possible, a piezoelectric power generation apparatus using a piezoelectric element that is displaced by a strong force can be realized. Even in such a case, sufficiently large electric energy can be obtained by using the piezoelectric element. Furthermore, it is possible to obtain electric power corresponding to the magnitude of the force applied to the holding unit 20 by connecting the piezoelectric power generation devices 100 in series and parallel.

  As the reinforcing plate 12 of the piezoelectric element 10, materials having various spring properties such as a resin substrate, a metal, and a metal plate can be generally used. For example, a metal plate having a predetermined strength is used as the reinforcing plate. Preferably used. When a large force is required for the holding member 21, a metal material such as engineering ceramics or stainless steel having excellent mechanical strength is preferably used.

  When the piezoelectric element 10 is deformed, a certain force is applied to the extended portion of the holding member. For this reason, the whole holding | maintenance part is calculated | required by the mechanical strength which does not raise | generate a deformation | transformation of holding | maintenance part itself when such force is applied. From such a viewpoint, various metal materials such as stainless steel and aluminum alloy are preferably used for the holding member.

  In the case where a metal material is used for the holding member and a metal material is also used for the reinforcing plate 12 constituting the piezoelectric element 10, a ceramic material having high mechanical strength and insulation as the holding member 20 (For example, alumina, zirconia, mullite, etc.) can be used.

  Furthermore, the holding member can hold three or more piezoelectric elements in the radial direction with the center of the holding member as the center of a substantially circle. FIG. 5 shows a piezoelectric power generation apparatus 200 in which four piezoelectric elements 10 are mounted in a cross shape. It is also preferable that a larger number of piezoelectric elements be mounted radially with the center of the holding portion being the center of the circle. FIG. 6 shows an example in which three fan-shaped piezoelectric elements are mounted radially.

In the piezoelectric generator 200 of FIG. 5 and the piezoelectric generator 300 of FIG. 6, the upper frame is not provided, or even if it is provided, the perforation diameter of the upper frame is set to be equal to or larger than the diameter of the holding portions 21a and 21b. Even for an external force having a component other than the direction perpendicular to the paper surface, an asymmetrical bending occurs in the piezoelectric element, and an electromotive force corresponding to the bending occurs in each piezoelectric element. Therefore, it is possible to separately extract the electromotive force from each piezoelectric element and detect the component other than the direction perpendicular to the paper surface of the external force and the magnitude of the electromotive force from the position information of each piezoelectric element and the measured value of each electromotive force. Become.

Furthermore, a plurality of piezoelectric elements having the same length as the piezoelectric plate can be held by the holding member and stacked in the thickness direction of the piezoelectric plate. That is, the plurality of piezoelectric elements can be mounted so that the plurality of piezoelectric plates are stacked in the extending direction of the holding member with or without the spacer. FIG. 7 shows an embodiment in which four piezoelectric elements are attached to the holding member 21c to which an external force acts via spacers 60, 60 ′, and the piezoelectric elements are bent. The thickness of the piezoelectric plate is such that a plurality of piezoelectric elements 13 are arranged on a holding member via spacers or at a fixed interval on one holding part, and when the piezoelectric elements are bent, they collide with each other to cause mechanical energy. It is preferable to arrange so that no loss occurs.

When the piezoelectric element 10 is deformed, a certain force is applied to the extended portion of the holding member and the spacer portion. For this reason, mechanical strength is required so that the spacer portion itself does not deform when such a force is applied. From such a viewpoint, various metal materials such as stainless steel and aluminum alloy are also preferably used for the spacer portion.

The holding members 21 and the spacers stacked in the extending direction are convenient for assembly if they are circular or regular polygons such as regular octagons. The piezoelectric element to be fixed may be chamfered with a piezoelectric plate or a reinforcing plate, as necessary, so that the end portion of the piezoelectric element can be satisfactorily engaged with the component of the holding portion. An external force can be transmitted to a plurality of radially arranged piezoelectric elements. If the displacement is the same, an electromotive force and a current proportional to the number of attachments can be obtained. If the deformation of each piezoelectric element is symmetric, there is no bias and stress concentration does not occur in part, so that it is robust and can have a long life.

In the piezoelectric power generation apparatus 100, a so-called bimorph structure in which the piezoelectric plate 11 is attached to one surface of the reinforcing plate 12 is shown as the piezoelectric element 13, but the piezoelectric plate 11 is disposed on one surface of the reinforcing plate 12, respectively. A so-called unimorph structure may be used. Furthermore, the piezoelectric plate is not limited to a single plate, and may have a multilayer structure (multilayer capacitor type structure).

  The electrical energy extracted from the piezoelectric power generation device 100 is used for charging a power storage device such as a battery or a capacitor.

Another embodiment of the piezoelectric power generation apparatus 400 will be described as an example. FIG. 10 is a front view of another piezoelectric power generation apparatus 400, and FIG. 11 is a plan view of another piezoelectric power generation apparatus 400. Compared to the piezoelectric power generation device 100, instead of the guide of the holding part 20 provided by drilling the frames 41, 41 ', four guide members 44 are provided on the frame 41'e, together with the drilling provided on the holding member 21e. , To guide. That is, the holding member 21e moves against the repulsive force of the elastic body in response to an external force, and moves along the four guide members 44 when the external force disappears and is displaced and bent by the repulsive force of the elastic body. At this time, the four guide members 44 are desirably metallic and coated with a tetrafluoroethylene polymer, and the holding member 21e is desirably a member having a small coefficient of friction such as a tetrafluoroethylene polymer. Also. A frictional force can be reduced by using a bearing at the contact portion with the guide member.

  As mentioned above, although embodiment of this invention has been described, this invention is not limited to such embodiment.

  The piezoelectric power generator according to the present invention is a compact power generator capable of obtaining a large electromotive force and large current and easy to maintain. It can also be used for signage and alarms in places where there is no power supply.

1 is a front sectional view showing a schematic structure of a neutral state of a piezoelectric power generation apparatus 100 according to the present invention. 1 is a front sectional view showing a schematic structure of a piezoelectric power generation apparatus 100 according to the present invention when pressurized. FIG. 6 is a front sectional view showing another schematic structure when the piezoelectric power generation apparatus 100 according to the present invention is pressurized. 1 is a plan view of a piezoelectric power generation apparatus 100 of the present invention. The top view of the piezoelectric part etc. of another piezoelectric generator 200. FIG. Furthermore, the top view of the piezoelectric part etc. of another piezoelectric generator 300. FIG. The schematic diagram which shows the structure of another piezoelectric part. An example of a circuit diagram. Another circuit diagram example. 1 is a front sectional view showing a schematic structure of a piezoelectric power generating apparatus 400 according to the present invention. FIG. 2 is a plan view showing a schematic structure of a piezoelectric power generating apparatus 400 according to the present invention. The schematic diagram of the electric power generation | occurrence | production condition of the piezoelectric generator 100 which concerns on this invention. An example of the generation | occurrence | production state of the electromotive force of the piezoelectric generator 100 which concerns on this invention.

Explanation of symbols

100/200/300/400: Piezoelectric generator
10, 10 ', 10a, 10a', 10b, 10b ', 10c, 10c'; Piezoelectric element
11,11 ', 11a, 11a', 11b, 11b ', 11c, 11c', 11d, 11d '; Piezoelectric plate
12 ・ 12´ ・ 12a ・ 12a´ ・ 12b ・ 12b´ ・ 12c ・ 12c´ ・ 12d ・ 12d´ ・ 12e ・ 12e´; Reinforcing plate
13, 13 ', 13a, 13a', 13b, 13b ', 13c, 13c', 13d, 13d ';
20; Holding part
21 ・ 21a ・ 21b ・ 21c ・ 21d ・ 21e; Holding member
22 ・ 22´ ・ 22a ・ 22b ・ 22c ・ 22d ・ 22e; Extension of holding member
23 ・ 23´ ・ 23a ・ 23b ・ 23c ・ 23d ・ 23e; Stopper
30; elastic body
31; coil spring
41; upper frame
41´ ； Lower frame
42; side frame
43; foot frame
44; guide member
60 ・ 60a; Spacer

Claims (4)

A substantially rectangular or substantially sector-shaped piezoelectric element having a piezoelectric plate and a reinforcing plate, wherein the piezoelectric plate is arranged and stuck in the thickness direction along the longitudinal direction or radial direction of the reinforcing plate. A piezoelectric element including:
A holding member that movably holds one end in the longitudinal direction or radial direction of the piezoelectric element;
An elastic body that contacts the holding member,
The other end in the longitudinal direction or radial direction of the piezoelectric element is fixed by another holding member,
When the elastic body is displaced by an external force applied to the holding member or the elastic body, the external force is removed, and when the elastic body returns to its original shape, the piezoelectric element is displaced to obtain electric energy. A piezoelectric power generation device. 2. The piezoelectric power generating apparatus according to claim 1, wherein the holding member that movably holds one end of the piezoelectric element in the longitudinal direction or the radial direction has a groove portion for receiving the reinforcing plate. 3. The piezoelectric power generator according to claim 1, comprising a plurality of piezoelectric elements, wherein the first holding member is arranged at the center of the circle, and a plurality of substantially identical piezoelectric plates are arranged radially from the center of the circle. . 4. The piezoelectric power generating apparatus according to claim 3, wherein an electromotive force is separately extracted from the plurality of piezoelectric elements, and a direction and a magnitude of an external force are detected from position information of each piezoelectric element and a measured value of the electromotive force.

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