JP2008245483A - Piezoelectric power plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric power plant for efficiently converting feeble rotational energy caused by natural force or artificial force into electric energy. <P>SOLUTION: The piezoelectric power plant has a piezoelectric plate and an elastic reinforcing plate. The power plant also has a piezoelectric element comprising the piezoelectric plate polarized, arranged and stuck in a thickness direction along a longitudinal direction of the reinforcing plate, a fixing member fixing one end in the longitudinal direction of the piezoelectric element, an external force translation rod which makes the piezoelectric element bend in the thickness direction, and a rotary part rotating by external force. One end of the external force translation rod is turnably held. The rotary part periodically depresses the rod and it moves. The rod transmits external force to the piezoelectric element and periodically bends it. Thus, power is generated. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a piezoelectric power generator that converts mechanical energy generated by rotation 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 respect 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 portion. 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 generator has the advantage that a large electromotive force can be obtained instantaneously with respect to mechanical energy due to vibration having a certain threshold, but it is difficult to obtain an electromotive force from relatively weak mechanical energy due to rotational force. There were disadvantages.

The present invention has been made in view of such circumstances, and an object thereof is to provide a piezoelectric power generation device that can efficiently convert weak rotational energy generated by natural force or artificial force into electrical energy. To do.

A substantially rectangular piezoelectric element having a piezoelectric plate and an elastic reinforcing plate, the piezoelectric element including a piezoelectric plate disposed and adhered in the thickness direction along the longitudinal direction of the reinforcing plate; and
A fixing member for fixing one end of the piezoelectric element in the longitudinal direction;
An external force transmission rod that bends the piezoelectric element in the thickness direction;
A rotating part that rotates by an external force;
Have
The external force transmission rod is rotatably held at one end, is periodically pressed and moved by the rotating portion, transmits an external force to the piezoelectric element, and is bent periodically to generate power. A piezoelectric power generator characterized by
The rotating part includes a rotating shaft and a plurality of rotating bodies fixed to the rotating shaft,
The force point at which the rotating body presses the external force transmission rod is at a longer distance from the holding point, which is the fulcrum of the external force transmission rod, than the action point at which the external force transmission rod presses the piezoelectric element, and transmits the external force to the piezoelectric element. When this is bent periodically, the force with which the external force transmission rod is pressed from the rotating body is suddenly removed from the rotating body, and the bending of the reinforcing plate of the piezoelectric element is restored by elastic force, and the piezoelectric element vibrates. The piezoelectric power generation apparatus is characterized in that electrical energy is obtained by displacing the piezoelectric element when returning to the original shape.

Furthermore, the piezoelectric power generation apparatus of the previous period is characterized in that the external force is a force from a windmill, and the rotation shaft of the rotating portion is interlocked with the axle of the windmill.

According to the piezoelectric power generation device of the present invention, an electromotive force is generated by a rotational force that is an external force periodically bending and displacing the rectangular piezoelectric element via the external force transmission rod. 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 weakly rotating mechanical energy generated by the above to a relatively large rotational energy. In addition, the number of parts is relatively small and assembly is easy.

Moreover, in the system of this invention, if it is a place which can obtain a wind force, this force can be utilized effectively anywhere, and an operation rate and power generation efficiency increase further. Effective use of unused energy is possible without relying on resources such as fossil fuels and nuclear power. It is also suitable as a maintenance-free power generator for warning and guidance display lighting in places where there is no power supply facility.

FIG. 1 shows a schematic structure of the piezoelectric power generation apparatus 100, and FIG. 2 shows a front sectional view showing a displacement state of the piezoelectric element 10. As shown in FIG. The piezoelectric power generation device 100 includes a piezoelectric element 10 formed by bonding a rectangular piezoelectric plate 11 and a rectangular reinforcing plate 12, a holding unit 20, an external force transmitting unit 30, and a rotating unit 40. One end of the rectangular piezoelectric element 10 is fixed to the holding portion 20. The other end of the rectangular piezoelectric element 10 is a free end. The external force transmission unit 30 holds one end of the external force transmission rod 31 so as to be rotatable by a rotation shaft 32. The external force transmission rod 31 is pressed from the rotating body 41 of the rotating unit 40 and tilts toward the piezoelectric element, and rotates while pressing and bending the piezoelectric element. The rotating body 41 rotates (revolves) while pressing the external force transmission rod 31. Even if the rotating body 41 loses contact with the external force transmission rod 31, it continues to rotate and repeats the operation of pressing the external force transmission rod 31 again. Then, this series of operations is continued. The rotating body 41 has a columnar shape having a shaft punching portion, and is provided with a shaft-shaped gap passing through a circular center portion of the bottom surface. A rotating body rotating shaft 43 is inserted into the gap in the previous period, and the rotating body 41 is pivotally supported so that it can rotate.

The driving mode of the piezoelectric element 10 is substantially determined by the shape and dimensions of the rotating unit 40 and the piezoelectric element 10, the position relative to the holding unit 20, and the external force transmitting unit 30. That is, as described above, the external force transmission unit 30 is rotatably held at one end of the external force transmission rod 31 by the rotation shaft 32, is pressed from the rotating body 40 of the rotation unit, and is inclined to the piezoelectric element side. However, if the transmission rod 30 is relatively long and the first contact position is the end portion of the piezoelectric element, the end portion is continuously pressed. On the other hand, as shown in FIG. 1, when the transmission rod is relatively short and the first contact position is not the end but the inside of the end of the piezoelectric element, the tip of the transmission rod 30 is the inside of the piezoelectric element. The piezoelectric element is pressed and bent while moving inwardly. Further, the distance from the rotation center 42 to the external force transmission portion, the length from the rotation center 42 to the rotating body 41, the angle of the piezoelectric element 10 with respect to the holding member 20, the length of the transmission rod 31, the piezoelectric element 10 and the external force transmission rod 31. The effect on the electromotive force varies greatly depending on the contact position and the like.

FIG. 2 illustrates a state in which the external force transmission rod 31 gives the maximum bending displacement to the piezoelectric element due to the external force of the rotating body 41. Thereafter, when the rotating body 41 further rotates in the clockwise direction, the external force transmission rod 31 is detached. The piezoelectric element released from the pressing force tends to be restored to the initial state by the elasticity of the reinforcing plate 12. This restoration may be reinforced by another elastic body (for example, an elastic body such as a coil spring, a leaf spring, or rubber that is restored in the direction opposite to the pressing direction). The shape of the piezoelectric element 10 is such that the reinforcing plate 12 has a substantially rectangular shape, and a substantially rectangular piezoelectric body 11 that is slightly smaller is attached to the reinforcing plate 12. The piezoelectric body 11 may have a monomorph structure attached to one side of the reinforcing plate, or may have a bimorph structure attached to both sides of the reinforcing plate. Moreover, it is not limited to a substantially rectangular reinforcing plate, and may be a fan shape, an inverted triangle, or the like having a length change in the width direction. One end of the piezoelectric element in the longitudinal direction is fixed and fixed by the holding unit 20. The holding part 20 can also serve as a holding part for the external force transmission rod 31. When an elastic body such as a coil spring is added, it is installed so that the restoring force of the elastic body acts on the vicinity of the free end of the external force transmission rod 30 and the free end of the piezoelectric element 10. At this time, when the rotating body 41 moves away from the external force transmission rod 31, the external force transmission rod 31 and the piezoelectric element 10 move in a direction to return to the initial state shown in FIG.

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. One having a structure in which a piezoelectric ceramic plate and a metal plate, a reinforcing plate such as plastic (hereinafter referred to as a reinforcing plate 12) are bonded together (for example, one corresponding to a needle driving unit of an electric knitting machine, a piezoelectric acoustic element of a piezoelectric speaker, These can be used as unimorph elements and bimorph elements). 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. Furthermore, the piezoelectric plate is not limited to a single plate, and may have a multilayer structure (multilayer capacitor type structure).

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. When 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 easily take out electrode leads (not shown) from the piezoelectric plate 11. It is preferable to use what is.

3 and 4 show an example of an embodiment of the present invention that obtains a natural rotational force from a windmill. The embodiment will be described in more detail by taking this embodiment as an example. In FIG. 3, the rotating shaft of the wind turbine propeller and the rotating shaft 42 of the rotating unit 40 are directly connected. One end of the external force transmission rod 31 is rotatably held by a rotation shaft 32. The rotational force generated by the windmill is transmitted to the rotating body 41 and the external force transmission rod 31 bends the piezoelectric element 10. FIG. 3 shows a state immediately before the rotating body 41 rotating in the clockwise direction contacts the external force transmission rod 31. The external force transmission rod 31 is set in an upright state in the initial state. When the rotating body 41 further rotates, the external force transmission rod 31 is swung to the left side and presses the external force transmission rod 31 until the state shown in FIG. One end of the reinforcing plate 11 is pressed. The rotating body 41 is pivotally supported by inserting the rotating body rotating shaft 43 and presses the external force transmitting rod 31 while rotating, so that the frictional force is reduced and the external force can be transmitted efficiently. In addition, when the external force transmission rod 31 is cylindrical, the contact portion with the rotating body 41 is close to point contact, and the frictional force can be further reduced.

As shown in FIG. 3, the distance from the fulcrum that is the center of the rotating shaft 32 of the external force transmission rod 31 to the force point that is the contact point with the rotating body 41 is shorter than the distance from the fulcrum to the contact point to the piezoelectric element 10. Therefore, the lever principle works, and the small rotational force of the rotating body 40 is expanded and transmitted to the piezoelectric element 10 to bend it. When the clockwise rotation further proceeds from the state of FIG. 4, the rotating body 41 comes off the transmission rod 31. At this time, if the elasticity of the reinforcing plate 12 is sufficient, the piezoelectric element 10 from which the pressing force has been released is restored to the initial state at once and freely vibrates. At this time, in addition to the elasticity of the reinforcing plate 12, this restoration may be performed by another elastic body (for example, an elastic body such as a coil spring, a leaf spring, or rubber inserted on the opposite side to the pressing direction).

The holding unit 20 and the rotating body support member 21 are desirably made of a material such as plastic or metal that has some rigidity and excellent durability. 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. When the holding part 20 and the rotating body support member 21 are metallic, they are conductors and can be used as part of the wiring. If contact with the electrical wiring system is disadvantageous, consider insulation. These may be integrally formed. The reinforcing plate 12 of the piezoelectric element 10, the rotating shaft 32 of the external force transmitting plate 30, and the rotating shaft 42 of the rotating unit 40 may be held together.

Further, the elastic body portion (not shown) can be configured by providing a coil spring or the like and a coupling portion end to the holding portion 20 and the rotating body support member 21 in order to hold the spring. A part of the coil spring or the like can be fixed to the end face of the holding member and the contact member can be omitted. The elastic body applies a repulsive force against the external force applied to the holding portion to accelerate the bending recovery of the piezoelectric element.

As shown in FIG. 3, the piezoelectric power generation apparatus 200 includes a rotating body 41 and an external force transmission rod 31 attached to a rotating body support member 21. The piezoelectric element 10 is attached to the holding unit 20 in a state of being inclined toward the rotating body support member. By this inclination, the force from the external force transmission rod 31 that is rotated and inclined can be transmitted in an efficient direction. In an initial state in which the piezoelectric element 10 is not bent, the external force transmission rod 31 is held in a state of substantially overlapping with the rotating body support member. FIG. 4B illustrates a rotating unit 42 in which a rotating shaft 42 is directly connected to a windmill shaft, and two rotating bodies 41 are attached in the diameter direction of a rotating orbiting circular orbit.

With respect to the neutral state piezoelectric power generation apparatus 200 illustrated in FIG.
, One of the rotating bodies 41 presses one end of the external force transmission rod 31, and the external force transmission rod 31 rotates around the rotation shaft 32 in the left direction of the drawing. At this time, the outermost end portion of the reinforcing plate 12 of the piezoelectric element 10 is pressed by the external force transmission rod 31. The outermost end portion is closer to the rotation axis than the contact point between the rotating body 40 and the external force transmission rod, which is a force point of external force. Therefore, according to the lever principle, the external force is applied to the piezoelectric element 10 as a relatively large external force. It can be transmitted.

The external force transmission rod 31 is made of a lightweight and rigid durable member such as engineering plastic, ceramics, metal or the like. In particular, it is desirable to use a lightweight and rigid metal hollow tube structure. This is because the restoration can be made promptly and easily. In the illustrated piezoelectric power generator 200, a hollow tube of aluminum alloy is used. FIG. 4A shows a state in which the external transmission rod 31 is rotated to the leftmost. The outermost end portion of the reinforcing plate 12 of the piezoelectric element 10 receives the external force, and the entire piezoelectric element 10 is bent most. When the rotating portion further rotates clockwise from this state and the rotating body 41 moves away from the external force transmission rod 31, the external force is lost rapidly. Then, the piezoelectric element 10 tries to restore the state of FIG. 3 by the elastic force of the reinforcing plate 11. At this time, the external force transmission rod 31 returns to the initial state of FIG. 3 due to the force to be restored. In order to prevent the external force transmission rod from excessively rotating in the right direction, the rotation support member 21 can be provided with a stopper (not shown) to stop the rotation.

Furthermore, in order to reinforce the elastic force of the reinforcing plate 12, another elastic body (for example, an elastic body such as a coil spring, a leaf spring, or rubber inserted on the side opposite to the pressing direction) can be installed. At this time, if the piezoelectric element 10 is bent and a gap is generated between the external force transmission rod 31 and the piezoelectric element 10, the bending of the piezoelectric element 10 is rapidly restored and further vibration occurs. While the unloaded state is maintained, this vibration continues until the rotating body 41 next presses the reinforcing plate 12 through the external force transmission rod 31 and continues the damped vibration. Subsequently, when an external force is applied, the damped vibration of the piezoelectric element is repeated at a constant period, 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. 5 shows a circuit configuration example for recovering electrical energy from the piezoelectric power generation apparatus 200.

For example, in the piezoelectric power generation apparatus 200, the piezoelectric plate 11 is rotated in the direction in which the external force transmission rod 31 obtained by converting the external force shown in FIGS. It will be a periodic displacement that bends and repeats unevenness. 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.

In the bimorph type piezoelectric element in which the polarization directions of the piezoelectric plates 11 arranged above and below the reinforcing plate 12 are parallel, the electrode on the bonding surface side of the piezoelectric plate opposite to the electrode film on the bonding surface side of the piezoelectric plate 11 is used. The structure which short-circuits a film | membrane 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 bonding surface side of the piezoelectric plate 11 and the electrode film on the bonding surface side of the piezoelectric plate on the opposite surface. There is a need. For this reason, 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 having a metal substrate attached to a resin substrate, such as a printed circuit board, the metal foil is connected to the inner peripheral side portion so that the piezoelectric plates disposed 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 electric energy thus obtained is AC power, as shown in FIG. 6, it is converted to DC power through a rectifier circuit and charged in a power storage device such as a capacitor or a secondary battery, or directly “load”. The load can also be driven by supplying to When a plurality of piezoelectric elements are used, direct current power can be obtained through a rectifier circuit for each piezoelectric element or by inserting a rectifier circuit for each piezoelectric element group. FIG. 7 specifically shows an example of the state of electromotive force generated by the rotational force of the windmill in the piezoelectric power generation apparatus 200 obtained by the circuit of FIG. This is an overlay of the results of three measurements. The reproducibility of the generation of electromotive force is relatively good. The first peak is unique to the example device, and is thought to be due to disturbance in the damping vibration of the piezoelectric element.

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 load is a light emitting diode, it emits light.

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.

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

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. FIG. 2 is a front sectional view showing a schematic structure when the piezoelectric power generation apparatus 100 according to the present invention is pressed. 1 is a front sectional view showing a schematic structure of a neutral state of a piezoelectric power generation apparatus 200 according to the present invention. FIG. 3 is a front sectional view showing a schematic structure when the piezoelectric power generation apparatus 200 according to the present invention is pressed. An example of a circuit diagram. An example of another circuit diagram. An example of an electromotive force generated by a rotational force generated by a windmill of the piezoelectric power generation apparatus 200.

Explanation of symbols

100 ・ 200; Piezoelectric generator
10: Piezoelectric element
11: Piezoelectric plate
12; Reinforcing plate
20; Holding part
21; Rotating body support member
30; External force transmission
31; External force transmission rod
40; rotating part
41; Rotating body
42; rotating part rotating shaft
43; Rotating body rotation axis

Claims (3)

A substantially rectangular piezoelectric element having a piezoelectric plate and an elastic reinforcing plate, the piezoelectric element including a piezoelectric plate disposed and adhered in the thickness direction along the longitudinal direction of the reinforcing plate; and
A fixing member for fixing one end of the piezoelectric element in the longitudinal direction;
An external force transmission rod that bends the piezoelectric element in the thickness direction;
A rotating part that rotates by an external force;
Have
The external force transmission rod is rotatably held at one end, is periodically pressed and moved by the rotating portion, transmits an external force to the piezoelectric element, and is bent periodically to generate power. A piezoelectric power generation device characterized by: The rotating part includes a rotating shaft and a plurality of rotating bodies fixed to the rotating shaft,
The force point at which the rotating body presses the external force transmission rod is at a longer distance from the holding point, which is the fulcrum of the external force transmission rod, than the action point at which the external force transmission rod presses the piezoelectric element, and transmits the external force to the piezoelectric element. When this is bent periodically, the force with which the external force transmission rod is pressed from the rotating body is suddenly removed from the rotating body, and the bending of the reinforcing plate of the piezoelectric element is restored by elastic force, and the piezoelectric element vibrates. The piezoelectric power generator according to claim 1, wherein when the piezoelectric element returns to its original shape, electric energy is obtained by displacing the piezoelectric element. 3. The piezoelectric power generator according to claim 1, wherein an external force is a force from a windmill, and a rotation shaft of the rotating portion is interlocked with an axle of the windmill.

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