JPH11146663A - Piezoelectric generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric generator which uses such a piezoelectric element that has a relatively simple constitution, is suitably carried due to its small size, thin thickness, and light weight, can highly efficiently make conversion, and can obtain relatively large energy. SOLUTION: A piezoelectric generator is provided with a lever section 2 having a free end which becomes the antinode of free oscillations and a supporting end which supports the free end and becomes the node of free oscillations, a weight 1 installed to the free end of the lever section 2, a laminated piezoelectric element 4 which is provided at a point of application between the free and supporting ends of the lever section 2 and pressurized by means of the oscillations of the weight 1 and the lever section 2, and an electrode through which the voltage generated in the element 4 due to the strain caused by the pressurization is taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generating device for converting mechanical vibration into electricity, and more particularly to a power generating device using a piezoelectric element for generating power by vibration generated with the movement of a user's body.

[0002]

2. Description of the Related Art Conventional power generation devices include:
An electromagnetic power generation device (application of the reverse principle of a motor) is common. Such an electromagnetic power generation device is configured by a motor (composed of a magnet, a rotor, and the like) and a reduction gear (gear), and it has been difficult to reduce the size, thickness, and weight. There is also an idea to use a piezoelectric element having a higher energy density than an electromagnetic motor as a power generator.

For example, as a small power supply device for a portable timepiece, there is known a small power generation device for a type in which a piezoelectric element is distorted by the movement of a rotating weight generated by the movement of a user to generate electric power. I have. If the battery can be charged using such a power generation device that automatically generates power only by moving the body, a wristwatch or the like can be semipermanently supplied with power and used continuously.

[0004] Such a power generation device can be applied to various electric devices to be worn or carried,
For example, it can be applied to a bell pager, a mobile phone, a wireless device, a hearing aid, a calculator, an electronic organizer, a radio, a TV receiver, an IC card, and the like, and is also attracting attention as an energy source of a micro robot. However, the piezoelectric element generates electric charges only when a force is applied, so that it is difficult to continuously extract electric charges. Further, since the output impedance is high, it is not very suitable for extracting electric current. For this reason, power generators using piezoelectric elements are not widely used.

As a power generating apparatus using such a piezoelectric element, for example, in Japanese Patent Application Laid-Open No. 9-182465, lithium niobate is used as a piezoelectric element, and the piezoelectric element is extended to the base of a vibrating piece having a cantilever structure. An alternating current is extracted from an electrode provided on the supporting end side of the resonator element.

However, in this conventional example, the conversion efficiency between strain energy and electric energy is not always sufficient.
In addition, since many piezoelectric elements are provided on the supporting end side for the purpose of efficiently taking in strain energy, the additional impedance and output impedance of the resonator element increase,
As a result, there has been a problem that the mechanical quality factor is lowered and it is difficult to obtain a sufficient power generation effect.

[0007]

As described above, conventional power generators of electromagnetic type have drawbacks in that they are small, thin and light, and those using piezoelectric elements have insufficient conversion efficiency. There is a problem that the energy obtained in a normal operation state is also small.

The present invention solves this problem, and has a relatively simple structure, and is small, thin, lightweight, suitable for portability, has high conversion efficiency, and uses a piezoelectric element using a piezoelectric element capable of obtaining relatively large energy. An object is to realize a power generation device.

[0009]

In order to achieve the above object, the present invention provides a mechanical vibration means having a free end serving as an antinode of free vibration and a support end supporting the free end and serving as a node of free vibration. A weight means provided at a free end of the mechanical vibration means, and a pressure point provided at an action point located between the free end and the support end of the mechanical vibration means, which is pressurized by the vibration of the mechanical vibration means. It is characterized by comprising a piezoelectric means and an electrode means for extracting a voltage generated in the piezoelectric means due to the strain caused by the pressurization.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a power generating apparatus according to the present invention will be described in detail with reference to the accompanying drawings. An object of the present invention is to realize a power generation device using a piezoelectric element that is small, thin, lightweight, and suitable for carrying. FIG. 1 shows a configuration diagram of a first embodiment of the piezoelectric power generating device of the present invention. Here, a configuration is adopted in which a longitudinal effect piezoelectric vibrator formed in a laminated structure is incorporated in a notch displacement enlarging mechanism made of metal such as steel. The cantilever of the notch displacement enlargement mechanism has a structure in which a weight is attached to the tip of the lever.

In FIG. 1, 1 is a weight, 2 is a lever,
Reference numeral 3 denotes a cutout portion, 4 denotes a laminated piezoelectric element, and 5 denotes a metal angle. The operation of this structure will be described with reference to FIG. When the user wears the piezoelectric power generating device, the weight 1 and the lever 2 at the distal end are appropriately and continuously shaken while walking or operating, and the vibration is repeated. It is sufficient that the amplitude of the vibration is about several microns at the position of the weight 1 at the tip. This vibration is transmitted to the laminated piezoelectric element 4 through a notch displacement enlarging mechanism applying the principle of leverage.

With the vibration, a force due to the motion acceleration and the mass of the weight 1 is applied. In this state, the force applied to the piezoelectric element 4 is the force applied to the weight 1 at the tip of the lever portion 2 × the displacement expansion ratio (based on the principle of leverage), and a relatively large force is applied. During the movement of the body, a force is continuously applied to the piezoelectric element 4, and the piezoelectric element 4 continues to generate electric charges, that is, continues to generate electric power. The electric charge generated by the piezoelectric generator is charged in a battery or an electric double layer capacitor.

Here, individual components of the piezoelectric generator shown in FIG. 1 will be briefly described.

1) Piezoelectric element (longitudinal effect laminated piezoelectric vibrator) 4 As the laminated piezoelectric element 4, a vertical effect laminated piezoelectric vibrator made of PZT (lead zirconate titanate) -based material is used. As the piezoelectric material, a material having a high mechanical quality factor Qm such as PZT is used. Once a force is applied to the tip of the lever portion 2, the piezoelectric power generation device continues to vibrate while attenuating at its resonance frequency for a while. At this time, the higher the material of Qm,
The Q of the resonance is high, and the vibration can be continued for a longer time. Further, in order to reduce the output impedance of the piezoelectric element, a laminated structure of a single-layer piezoelectric element is employed.

2) Notch Displacement Enlarging Mechanism In order to increase the force applied to the lever tip, a displacement enlarging mechanism based on the principle of leverage is used. A metal (steel or the like) is used as a material of the angle 5 constituting the lever portion 2, the notch portion 3, and the like of the displacement magnifying mechanism. A cutout is made in a part of the metal angle 5 so that the lever 2 vibrates around the cutout 3 as a fulcrum. Since the weight 1 is attached to the tip of the lever portion 2, the lever tip portion of this mechanism vibrates due to the movement of the user's body such as when the user is walking.

At this time, the distance L1 from the fulcrum of the notch 3 to the weight 1 at the tip of the lever 2 and the distance L2 between the fulcrum of the notch 3 and the point of force applied to the laminated piezoelectric element 4 to which a force is applied, The force is expanded in accordance with the displacement expansion ratio L1 / L2, and the expanded force P is applied to the laminated piezoelectric vibrator. That is, assuming that the force applied to the weight 1 is P1, P = P1 × L1 / L2.

Further, since the notch 3 is provided in the angle 5 as a fulcrum as shown in FIG.
Energy loss in this part is reduced. Further, since the stiffness of this portion can be reduced by simply providing the notch portion 3 in the angle 5 and the vibration mode having almost one degree of freedom can be fixed, the production is very easy and the production can be performed at low cost. it can.

FIG. 2 shows a configuration diagram of a second embodiment of the piezoelectric power generating apparatus of the present invention. In FIG. 2, 1 is a weight,
21 is a first lever portion, 22 is a second lever portion, 3 is a cutout portion, 4 is a laminated piezoelectric element, and 5 is a metal angle. For convenience, the same functions as in FIG. 1 are given the same numbers. This embodiment is an example in which the displacement magnifying mechanism is a differential two-stage displacement magnifying mechanism. In this case, the first lever portion 2
Since the total length of the first and second lever portions 22 is further increased, the displacement enlargement ratio is further increased.

That is, the length of the first lever portion 21 is L
3. The length of the second lever portion 22 is L4, and the total distance from the fulcrum of the notch portion 3 to the weight 1 at the tip of the lever portion 2 is L1.
= L3 + L4, and the distance L2 between the fulcrum of the notch 3 and the point of force applied to the laminated piezoelectric element 4 where the force is applied, the force P applied to the laminated piezoelectric vibrator is P1 when the force applied to the weight 1 is P1. P1 × L1 / L4 × L4 / L2 = P1 × L1 / L2, and the force is enlarged according to the displacement enlargement ratio L1 / L2. The reason why the first lever portion 21 is bent at right angles to the second lever portion 22 is to make the overall shape smaller.

FIG. 3 shows a configuration diagram of a third embodiment of the piezoelectric power generating apparatus according to the present invention. In FIG. 3, 1-1 and 1-2 are weights, 2-1 and 2-2 are lever parts,
Reference numerals 1 and 3-2 denote cutout portions, reference numeral 4 denotes a laminated piezoelectric element, and reference numeral 5 denotes a metal angle. For convenience, components having the same functions as those in FIGS. 1 and 2 are denoted by the same reference numerals. In this embodiment, the lever portions 2-1 and 2-2 are provided at two positions as shown in the figure, and weights 1-1 and 2-1 are provided at the tips of the two lever portions 2-1 and 2-2, respectively. 1-2 are added. As described above, the tip 2 of the lever portions 2-1 and 2-2
Since a force is applied to the piezoelectric element 4 from the weights 1-1 and 1-2, more electric power is generated.

FIG. 4 is a structural view of the laminated piezoelectric element used in the embodiment of the present invention. Fig. 4 shows the multilayer piezoelectric element.
As shown in FIG. 4 (a), a plurality of piezoelectric ceramics 14, which are single-layer piezoelectric elements, are stacked.
As can be seen from the external view of (a) and the configuration diagram of FIG. 4 (b), the internal electrodes 12 are provided between the single-layer piezoelectric elements 14, and the external electrodes 11 are provided on the side surfaces of the stacked elements. A lead wire 13 for extracting the generated voltage is led from the electrode 11. According to such a configuration, it is possible to realize a piezoelectric power generation device which has a low output impedance and a large current, and is suitable for charging and using a capacitor.

FIG. 5 is a block diagram showing the configuration of a power supply circuit using the piezoelectric power generating device of the present invention. The AC output from the piezoelectric generator 30 is full-wave rectified by the diode bridge 31 and, after the rectification, the electric charge is stored in the electric double-layer capacitor 32 and output.

As described above, the present invention has been described according to some embodiments. However, the present invention is not limited to such embodiments, and various other configurations can be considered. . For example, in the embodiment, an example is shown in which the mechanical vibration system has a configuration in which a weight is attached to a cantilever, but any configuration can be used as long as the system can provide vibration close to a one-degree-of-freedom system. Further, although the laminated piezoelectric element is shown as a laminated type of a longitudinal effect piezoelectric vibrator, it is needless to say that a lateral effect piezoelectric vibrator can be used. With such a configuration, it can be used as a power source for various electric devices that are carried and used by humans, and can be charged to extend the life of the battery,
The battery itself can be dispensed with. Therefore, the user can use the portable electric device without worrying about running out of the battery, which is suitable for use in a disaster or a remote place, and is highly valuable as an energy-saving power source and an environmentally friendly power source.

[0024]

As described above, according to the first aspect of the present invention, there is provided a mechanical vibration means having a free end serving as an antinode of free vibration and a supporting end supporting the free end and serving as a node of free vibration. Weight means provided at the free end of the mechanical vibrating means, and piezoelectric means provided at an action point located between the free end and the support end of the mechanical vibrating means and pressurized by the vibration of the mechanical vibrating means, Electrode means for extracting a voltage generated in the piezoelectric means due to the strain caused by the pressurization. As a result, it is possible to realize a power generation device that is small, thin, lightweight, portable, has high conversion efficiency, and can obtain relatively large energy.

Further, the invention according to claim 2 of the present invention is characterized in that the piezoelectric means is a laminated piezoelectric element formed by laminating a plurality of single-layer piezoelectric elements. As a result, it is possible to realize a piezoelectric power generator having a low output impedance and a large current capacity.

Further, the invention according to claim 3 of the present invention is characterized in that the piezoelectric means is constituted by a piezoelectric element using a lead zirconate titanate-based material. This makes it possible to realize a piezoelectric power generation device with good energy conversion efficiency.

According to a fourth aspect of the present invention, the mechanical vibration means is formed of a metal structure having a cut in one place and the cut portion serving as a support end. Thus, the mechanical vibration means can be configured by a relatively simple and easy method, and the cost can be reduced.

As described above, according to the present invention, when the user is wearing a small, thin, and lightweight body, the power is continuously generated by the operation of the user, and the charge generated by the power generation is charged into a battery or the like. Therefore, it is possible to realize an energy-saving and environmentally-friendly power supply at a low price, which can use the portable electric device semipermanently and is suitable for use in a disaster or in a remote place.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment of a piezoelectric power generating device according to the present invention.

FIG. 2 is a configuration diagram of a second embodiment of the piezoelectric power generating device of the present invention.

FIG. 3 is a configuration diagram of a third embodiment of the piezoelectric power generating device of the present invention.

FIG. 4 is a structural view of a laminated piezoelectric element used in an embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of a power supply circuit using the piezoelectric power generation device of the present invention.

[Explanation of symbols]

Reference numerals 1, 1-1, 1-2: weight, 2, 2-1, 2-2: lever portion, 3-1, 3-2, notch portion, 4: laminated piezoelectric element, 5: metal angle, DESCRIPTION OF SYMBOLS 11 ... External electrode, 12 ... Internal electrode, 13 ... Lead wire, 14 ... Single layer piezoelectric element, 21 ... 1st lever part, 22 ... 2nd lever part, 30 ... Piezoelectric power generation device, 31 ... Diode bridge, 32 ... Electric double layer capacitor.

Claims (4)

[Claims] A mechanical vibration means having a free end serving as an antinode of free vibration and a support end supporting the free end and serving as a node of free vibration; and a weight means provided at a free end of the mechanical vibration means. A piezoelectric means provided at an action point located between the free end and the support end of the mechanical vibration means, and pressurized by the vibration of the mechanical vibration means; And an electrode means for extracting a voltage generated in the means. 2. The piezoelectric power generating apparatus according to claim 1, wherein said piezoelectric means is a laminated piezoelectric element formed by laminating a plurality of single-layer piezoelectric elements. 3. The piezoelectric power generating apparatus according to claim 1, wherein said piezoelectric means is constituted by a piezoelectric element using a lead zirconate titanate-based material. 4. The mechanical vibration means is formed of a metal structure having a cut in one place and the cut portion serving as the support end.
4. The piezoelectric power generating device according to claim 1.