JP2006216898A - Piezoelectric generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low-cost piezoelectric generator that makes natural oscillations of a piezoelectric element less prone to be transferred to other structures to thereby convert kinetic energy of several hertz into high-efficiency electric energy. <P>SOLUTION: One piezoelectric element 1 is fixed to one end of a coil spring or a plate spring 2, with the other end of the spring being supported by a housing 4. As a result, a structure is provided in which the natural oscillations of the piezoelectric element 1 are less prone to be transferred to other structures. The fixation of the piezoelectric element 1 to the spring enables continuous swinging as well as the efficient conversion of the kinetic energy of several hertz into electric energy. In addition, the piezoelectric element 1 serves as an impactor, and collides against the housing 4 which is provided with a projection 3 disposed to convert the kinetic energy which is produced during collision into electric energy, thus providing the simply structured low-cost piezoelectric generator. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric power generation apparatus using a piezoelectric element.

  A piezoelectric element is an element which has a piezoelectric property by generating remanent polarization by applying a DC high voltage to a polycrystalline body. Since the basic piezoelectric constant can be freely changed depending on the type of material and the composition of the material, its application is diverse. In particular, the lead zirconate titanate-based piezoelectric ceramic element has a wide composition ratio and a wide selection range of additives, and has a wide range of applications.

  When power is generated using such a piezoelectric element, an electrode is formed on the pair of surfaces having the widest area of the plate-like element and polarized, and an impactor such as a metal sphere or a ceramic sphere collides with one side of the piezoelectric element. The other surface is fixed, the opposite surface is pressed and deformed, and power is generated by utilizing the strain of the element orthogonal to the polarization direction of the piezoelectric element. The generated electric power is used for light emission of the light emitter and used for charging the secondary battery. For example, this power generator is attached to a shoe sole, and an impact body that moves by reciprocating left and right or up and down according to the movement of walking or running impacts the piezoelectric element, and generates electricity by the strain received by the piezoelectric element. Patent Document 1 discloses an invention in which a light emitter is caused to emit light using the electricity.

  Further, Patent Document 2 discloses an invention in which a light emitting diode built in a fishing lure is caused to emit light by using an electromotive force generated when an impact body moving by a reciprocating motion of a lure strikes a piezoelectric element.

  In the piezoelectric power generation device used in the above-described invention, two piezoelectric elements are used, one side of each piezoelectric element is fixed to the housing, and an impact body moves and strikes the piezoelectric element so that the piezoelectric element is distorted. Therefore, there is a problem that the natural vibration of the piezoelectric element is easily transmitted to other structures. For this reason, there are problems such that sufficient power generation efficiency cannot be obtained, or power generation cannot be performed unless the applied frequency is several tens of hertz or higher.

Japanese Patent Laid-Open No. 2001-204507 JP 2001-224281 A

  The present invention has been made to solve the above-described problems, and its technical problem is to make it difficult to transmit the natural vibration of a piezoelectric element to another structure, thereby to transfer kinetic energy of several hertz to highly efficient electric power. It is to provide a low-cost piezoelectric power generation device that converts energy.

  In order to achieve the above object, the first invention is a piezoelectric unimorph element obtained by joining plate-like piezoelectric ceramics to a plate-like elastic body, or two plate-like piezoelectric ceramics are joined directly or sandwiching a plate-like elastic body. In the piezoelectric power generation apparatus using a piezoelectric bimorph element, the piezoelectric unimorph element or an end of the piezoelectric bimorph element is fixed to one end of an elastic body, and the other end of the elastic body is supported by a housing, and the piezoelectric unimorph element Alternatively, a convex body is disposed at a position where it collides with the piezoelectric bimorph element by swinging, and the convex body is a piezoelectric power generation device that is joined to the housing or formed as a part of the housing.

  A second invention for achieving the above object is a piezoelectric power generator in which the elastic body is a coil spring or a leaf spring.

  A third invention for achieving the above object is a piezoelectric power generator in which the convex body is made of metal or ceramics.

  One piezoelectric element is fixed to one end of a coil spring or a leaf spring, and the other end of these springs is supported on the housing, so that the natural vibration of the piezoelectric element is not easily transmitted to other structures. By fixing to the spring, it becomes possible to continuously swing, and it is possible to efficiently convert kinetic energy of several hertz into electrical energy.

  In addition, a single piezoelectric element has a simple structure by using a piezoelectric element as an impact body and hitting a housing having a convex body arranged to convert kinetic energy at the time of collision into electrical energy. A low-cost piezoelectric power generation device can be provided.

  Furthermore, by making the material used for the convex body a metal or a ceramic with high hardness, it is possible to efficiently convert kinetic energy of several hertz into electrical energy by strengthening the impact on the piezoelectric element. .

  As a result, it is possible to provide a low-cost piezoelectric power generation device that can efficiently convert kinetic energy of several hertz into electrical energy.

  The piezoelectric element used in the piezoelectric generator according to the best mode for carrying out the present invention is a piezoelectric unimorph element obtained by joining plate-like piezoelectric ceramics to a plate-like elastic body, or two plate-like piezoelectric ceramics directly or on a plate. Piezoelectric bimorph elements joined with a cylindrical elastic body interposed therebetween. The piezoelectric element is preferably lead zirconate titanate or barium titanate.

  The piezoelectric element is fixed to one end of the plate-like elastic body, and the other end of the plate-like elastic body is fixed to the fixing portion of the housing, so that the convex portion can collide when the piezoelectric element swings. Arranged in the housing. The plate-like elastic body may be a coil spring or a leaf spring.

  Further, the material of the convex portion is desirably a metal having a function of giving an impact to the piezoelectric element or a material having high hardness such as ceramic, and the whole may be manufactured from the same material.

  Next, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view of a piezoelectric power generator according to an embodiment of the present invention. FIG. 2 is a perspective view showing a piezoelectric unimorph element according to an embodiment of the present invention. FIG. 3 is a perspective view showing a piezoelectric bimorph element according to an embodiment of the present invention. FIG. 4 is a cross-sectional view illustrating a state during power generation of the piezoelectric power generation apparatus according to the embodiment of the present invention. FIG. 5 is a circuit diagram of the piezoelectric generator according to the embodiment of the present invention.

  The piezoelectric element 1 is fixed to one end of the leaf spring 2 and the other end is fixed to the fixing portion 5 of the casing 4, and the convex portion 3 can collide when the piezoelectric element 1 swings. 4 was placed. The piezoelectric element 1 was made of lead zirconate titanate piezoelectric ceramics. The piezoelectric element 1 was connected to the terminals 14 and 15 with lead wires 10 and 11.

  The piezoelectric element 1 is a plate-shaped piezoelectric unimorph element obtained by bonding a plate-like piezoelectric ceramic 6 to a plate-like elastic body 7 as shown in FIG. 2 or two pieces of a plate-like piezoelectric ceramic 6 as shown in FIG. Any piezoelectric bimorph element joined with the elastic body 7 interposed therebetween may be used. The piezoelectric bimorph element may not have the plate-like elastic body 7.

  FIG. 4 is a diagram illustrating a state in which the convex portion 3 and the piezoelectric element 1 collide. By setting the resonance frequency formed by the leaf spring 2 and the piezoelectric element 1 to several hertz, when the housing 4 swings in the vicinity of the set resonance frequency, the piezoelectric element 1 collides with the convex portion 3 and the piezoelectric element 1 is distorted. Occurs. This strain causes a potential difference between the electrode 8 and the electrode 9 of the piezoelectric element 1. The electromotive force generated here was taken out with lead wires 10 and 11 and used as electric energy. Since this operation lasts as long as the oscillation continues, electric power can be generated continuously as long as the oscillation continues, and electric energy can be extracted more efficiently. Here, by attaching the piezoelectric element 1 to one end of a rubber plate which is a plate-like elastic body, a structure in which the natural vibration of the piezoelectric element is difficult to be transmitted to other structures becomes possible, and continuous oscillation is possible. Hertz's kinetic energy can be efficiently converted into electrical energy.

  Further, it has been found that the material of the convex portion is preferably a metal having a function of giving an impact to the piezoelectric element or a material having high hardness such as ceramic. Furthermore, it has been found that it is better to manufacture the entire housing 4 from the same material. When soft rubber was used, the impact force received by the piezoelectric element 1 was reduced to absorb the impact, and power generation was not possible. Moreover, when the same case as the case where the material of the housing | casing 4 and the convex part 3 is changed is compared, it turned out that it is better to manufacture with the same material since vibration is absorbed only by the difference in the restitution coefficient of material.

  In the power generation unit of the embodiment, an AC voltage is generated. Therefore, in a circuit as shown in FIG. 5, if necessary, rectification is performed with 12 rectifier circuits to extract a DC voltage, and 13 capacitors are connected to the load. The generated voltage was smoothed by connecting in parallel.

  The same effect was obtained even when a coil spring was used instead of the leaf spring 2.

1 is a cross-sectional view of a piezoelectric power generator according to an embodiment of the present invention. The perspective view which shows the piezoelectric unimorph element based on the Example of this invention. The perspective view which shows the piezoelectric bimorph element which concerns on the Example of this invention. Sectional drawing which shows the state at the time of the electric power generation of the piezoelectric power generator which concerns on the Example of this invention. 1 is a circuit diagram of a piezoelectric power generator according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Leaf spring 3 Convex part 4 Housing | casing 5 Fixing part 6 Piezoelectric ceramics 7 Plate-like elastic body 8 and 9 Electrode 10 and 11 of piezoelectric element Lead wire 12 Rectifier circuit 13 Capacitor 14 and 15

Claims (3)

  In the piezoelectric power generation apparatus using a piezoelectric unimorph element obtained by joining plate-like piezoelectric ceramics to a plate-like elastic body, or a piezoelectric bimorph element obtained by joining two plate-like piezoelectric ceramics directly or sandwiching a plate-like elastic body, The end of the unimorph element or the piezoelectric bimorph element is fixed to one end of an elastic body, and the other end of the elastic body is supported by a casing and protrudes to a position where it collides with the piezoelectric unimorph element or the piezoelectric bimorph element by swinging. A piezoelectric power generation device, comprising: a body, wherein the convex body is joined to a housing or formed as a part of the housing.   The piezoelectric generator according to claim 1, wherein the elastic body is a coil spring or a leaf spring.   2. The piezoelectric power generator according to claim 1, wherein the convex body is made of metal or ceramics.

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