JP2011233851A - Piezoelectric power generating unit and piezoelectric power generation mat applying it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generation unit and a power generation mat which has a breakable piezoelectric bimorph mounted as an piezoelectric element, which has water resistance, toughness, and high power generation performance, which can easily be instituted and wire-connected, and which can perform power generation operation sensitively detecting oscillation and pressure.SOLUTION: On one side of an elastic plate 1-2 made of rectangular insulator with the metalized sides, the ceramic sides of two piezoelectric unimorphs glued to a rectangular piezoelectric ceramics plate 1-1 shorter than the elastic plate in the long direction are glued facing inside with a spacer in-between made of insulator having a certain thickness and a purse on both sides of the longitudinal direction of the elastic plate, having such an organic material as silicone rubber and elastomer filling in the opposite gap. Also, the unit of this configuration is bedded in one or multiple steps as a tile in order to improve output power.

Description

The present invention relates to a piezoelectric power generation unit that converts intermittently obtained mechanical load, vibration, and the like into strain of a piezoelectric material and extracts electric energy therefrom, and a power generation mat using the piezoelectric power generation unit.

The present invention relates to a power generation device that utilizes electrical energy generated when a piezoelectric material is deformed or vibrated by an external force, and its features are that it functions as a power generation device as long as it has mechanical inputs such as vibration and impact. The present invention relates to a piezoelectric power generation unit capable of storing the electric power directly or in a capacitor, a secondary battery or the like and taking out electric energy as required, and a piezoelectric power generation mat using the piezoelectric power generation unit.

Attempts have been made to use electrical energy generated when a piezoelectric material is distorted. As means for obtaining electric energy from the piezoelectric element, usually, an impact body such as a metal sphere or ceramic sphere collides with the piezoelectric element, or one end of the piezoelectric element is fixed and the opposite end is pressed and deformed. Electric power is generated by distortion of the piezoelectric element. The electric power generated at this time is used for the light emission of the light emitting diode, or the secondary battery is charged and used as needed to drive the signal processing device.

Cited Document 1 proposes a pendulum type power generation device that generates electric power by receiving vibration during walking by incorporating a piezoelectric bimorph having a cantilever structure into a unit.
Cited Document 2 proposes a building floor board material incorporating a piezoelectric ceramic and having a power generation function.
In Cited Document 3, a proposal is made that a pressing power generation element is arranged on the floor around the staircase and the staircase and used for illumination of the staircase.
Cited Document 4 proposes a power generation system in which a plurality of piezoelectric elements are three-dimensionally combined to improve power generation capability, and a road surface plate incorporating the piezoelectric element generates power by pressure change due to passage of a vehicle or a pedestrian.
Cited Document 5 also proposes a power generation block in which a piezoelectric element is incorporated in a block provided on a road surface and a light emitting diode blinks.
JP-A-2005-319013 JP-A-5-39661 Japanese Patent Application No. 10-163095 JP 2006-32935 A JP20080126767

As described above, many proposals have been made to incorporate a piezoelectric element in an outdoor facility and use a pressure change during passage of a passerby or a vehicle for power generation. The point that is mainly required for the power generation unit part of the system applied to road surface guidance etc. by attaching the piezoelectric element inside the outdoor facility and receiving the pressure at the time of walking is blinking the light emitting diode,
・ Fully absorbs mechanically acting impact force and pressure and has high power generation efficiency. ・ It is mechanically robust and is not easily damaged. ・ Structure with sufficient consideration for water resistance. ・ Simple structure that is easy to make. It is important for practical use to be easy to construct

Cited Document 2 introduces a configuration in which a plurality of columnar piezoelectric elements are arranged between block-shaped plates provided as a floor plate, and the piezoelectric elements receive pressure in the axial direction. Therefore, the amount of distortion generated by receiving a load is small and the power generation efficiency is not necessarily good. In piezoelectric power generation that uses pressure changes during passage of people or vehicles for power generation, piezoelectric bimorphs and piezoelectric unimorphs that are easily distorted with relatively little force, that is, low compliance, are mainly used. Here, the difference between the piezoelectric bimorph and the piezoelectric unimorph is the difference between whether the piezoelectric element is attached to one side or both sides of the elastic material, and may be appropriately selected according to the purpose. It utilizes the characteristics of a certain piezoelectric unimorph.

Piezoelectric bimorphs or piezoelectric unimorphs with low compliance fall into the category of piezoelectric elements that are mechanically weak and fragile. Therefore, it is desirable to provide a unit that is robust and easy to handle in a system utilizing these. In consideration of measures against damage, the cited document 4 and the cited document 5 are designed such that the constituent member plays the role of a stopper so that the deformation of the piezoelectric bimorph subjected to external force can be suppressed within a certain value.

When a piezoelectric bimorph is applied to power generation, it is a structural requirement to ensure a certain gap for generating a displacement under a load. Cited Document 5 introduces a cantilever type bimorph configuration in which one end of a piezoelectric bimorph is fixed to a side wall of a casing forming a block and a load is received at the other end located in the center. When the unit is mounted on the side wall, the arrangement becomes three-dimensional and the number of assembling steps tends to increase. In particular, in this type of application, a plurality of bimorph elements are often incorporated in order to ensure the amount of power generation, in which case this problem becomes more realistic.

The present invention has been made in view of such circumstances, and as a piezoelectric element, a power generation unit incorporating a piezoelectric bimorph that is easily damaged is water-resistant and robust and has high power generation performance, and facilities and connections are easy. An object of the present invention is to provide a power generation unit capable of sensitively detecting vibration and pressure and generating power.

According to the first aspect of the present invention, a piezoelectric material in which a rectangular piezoelectric ceramic plate slightly shorter than the elastic plate in the length direction is attached to one surface of an elastic plate made of a rectangular insulator metallized on both sides. There is provided a piezoelectric power generation unit characterized in that two unimorph ceramic sides are bonded to each other in the longitudinal direction of the elastic plate with spacers made of an insulator having a certain thickness and width facing each other inward. The

According to a second aspect of the present invention, the two poles formed of the outer metallized surface and the two poles connected in parallel or in series with respect to the two piezoelectric unimorphs are connected by a full-wave rectifier circuit. One piezoelectric power generation unit is provided.

According to a third aspect of the present invention, there is provided the piezoelectric power generation unit according to claim 1 or 2, wherein an organic material such as silicon rubber or elastomer is filled in a gap between two piezoelectric unimorphs facing each other. Provided.

According to a fourth aspect of the present invention, only the base portion in the lengthwise direction of the power generation unit according to claim 3 is hard, and the other portions are made of a material that is easily elastically deformed, such as rubber. There is provided a piezoelectric mat characterized in that the power generation unit is laid on the top.

According to a fifth aspect of the present invention, the power generation unit according to claim 3 is electrically connected by stacking a plurality of stages in the thickness direction while shifting by half the length in the length direction. A piezoelectric power generation mat is provided.

Power generation by the piezoelectric bimorph is performed by the strain generated by the piezoelectric element as the deformation progresses within the critical point of breakage first, and then the elastic system including the piezoelectric bimorph accumulates after the load is removed. The piezoelectric element is stimulated again by the impact vibration generated in the process of releasing the energy and generates distortion.
It is easy to create a system that can ensure a certain amount of displacement with respect to the piezoelectric element with a relatively large mechanical amount of load, vibration, or impact due to a person walking or passing a vehicle.
The amount of energy E stored in the elastic system is K when the spring constant of the system receiving the load is K and the displacement is δ.

As can be seen from the above equation (1), if it is assumed that a constant amount of displacement δ can always be secured by using an external load, the stored energy E can be obtained by increasing the spring constant K as much as possible within the possible design range. This is advantageous for the power generation unit. As described above, it has been explained that small compliance of the bimorph element is advantageous for power generation. However, if the external force is large and the displacement δ can be sufficiently secured, if the compliance is adjusted to a large extent as much as possible, the stored energy E is large and the power generation is efficient. Become a unit.

In principle, the cantilever type with a bimorph element support method has the smallest compliance and is easy to react even with a weak force.To adjust this compliance greatly, increase the thickness of the bimorph element or increase the effective length of the element. This can be achieved by shortening. However, it was confirmed that the distortion generated in the vicinity of the fixed part was increased and the ceramic was easily damaged and inferior in durability.
In addition, when the bimorph element is a double-sided support beam type, the compliance can be increased. However, in this case, it has been found that instability in fixing cannot be avoided and consequently stable power generation performance cannot be obtained.
Compliance can be maximized for the bimorph element fixed both ends type. However, when a load is applied, a place where positive and negative bending moments occur on the beam (piezoelectric bimorph) is generated near both ends, so that it is conceivable that the charge generated on the electrode surface is canceled. Therefore, by adjusting the ceramic length to be shorter than the span length, it is possible to select a range in which a bending moment having the same sign is generated in the ceramic.
In this case, it has been found that a double-ended support configuration is preferred for this purpose.

As a result of intensive studies, the inventors attached a rectangular piezoelectric ceramic plate slightly shorter than the elastic plate in the length direction to one side of an elastic plate made of a rectangular insulator that is electrically separated and metallized on both sides. The inventors have come to invent a structure in which two ceramic unimorphs attached to each other are bonded to each other in the longitudinal direction of the elastic plate through spacers made of an insulator having a constant thickness and width toward the inside.

Further, the two piezoelectric unimorphs are in parallel connection if importance is placed on current output, and if the importance is placed on voltage output, two poles consisting of two terminals connected in series and the outer metallized surface are invented by a full-wave rectifier circuit. It came to. Furthermore, it has been found that it is effective if the lower surface side of this unit is only on the center part and the rest is on an elastically soft base material.

This configuration will be described. As shown in FIG. 1, when the load is received, the upper and lower central portions are bent inward to generate elastic deformation, and when the load is released, the piezoelectric element is deformed again by the stored elastic energy to generate power. In the process, the charge inside the elastic plate is reversed between positive and negative. FIG. 2 shows a case where two unimorphs are connected in parallel. The electrodes facing the inside of the electric charges generated by the upper and lower piezoelectric elements are mutually connected with the electrodes inside the elastic plate facing each other, but both electrode surfaces connected by adjusting the polarization direction generate the electric charges with the same sign, This sum of charges is stored on the inner facing metallized surfaces. Therefore, as shown in FIG. 2, when the inner metallized electrode is two poles and a full-wave rectifier circuit is connected between the two outer metallized surfaces, the outer electrode always obtains electric output from the same electrode surface with the same sign. The upper and lower metallized surfaces can function as DC output terminals.

Finally, in order to improve moisture resistance, the gap between the two piezoelectric unimorphs was filled with an organic material such as silicon rubber or elastomer. Although the water resistance was greatly improved by this treatment, the power generation performance was hardly deteriorated. This is considered to be because the bending elastic modulus of the composite beam composed of the piezoelectric ceramic and the elastic substrate is not affected because there is a difference of 5 digits or more compared to the bending elastic modulus of the filled organic material.

Next, a power generation mat configured by combining a plurality of power generation units described above will be described. Spread the power generation unit on the rectangular base on the front, back, left, and right tiles. The base is entirely made of a material that is easily elastically deformed, such as rubber or elastomer, but a rigid body that is difficult to elastically deform in a line shape is formed in the base. The power generation unit is arranged so that this rigid body just crosses the center. Although both ends of the spacer cannot be deformed with respect to the load from above, the central portion receives the load from above and from below, and each elastic plate is bent into a concave lens shape to generate power efficiently.

It is also effective to stack a plurality of layers in the thickness direction for the purpose of increasing the amount of power generation. In this case, if the position is shifted in the length direction by half of the total length for each step, the end of the unit that is not elastically deformed in the lower unit comes directly under the center after the second step. A concave lens-like deformation is promoted and efficient power generation becomes possible.

When only one layer is laid, a part of the parallel connection of a plurality of units can be configured by making the rigid body contacting the center of the lower electrode directly contact with a metal such as copper or aluminum. In addition, by arranging a plurality of metal foils on the upper surface or partly, a desired connection, for example, a parallel connection between specific units can be configured.

In the case of stacking in the thickness direction, if the units are in direct contact, the same series connection as that of the dry battery is possible and the generated voltage increases. In the case of stacking, when the metal foil and the insulating sheet are used in a stacked state, parallel connection between the units stacked in the thickness direction is also possible. Thus, it can be seen that when the features of the configuration of the present invention are effectively used, an efficient power generation mat can be realized by simply connecting a plurality of units.

Power generation unit that is water-resistant and robust, has high power generation performance, easy facility and connection, can detect vibration and pressure sensitively, and can generate power, and can be arranged and connected easily by combining multiple power generation units. Power generation mats can be provided.

Example 1
Next, embodiments based on the claims will be described in detail.
FIG. 3 shows a perspective view and a sectional view of the piezoelectric power generation unit according to the present invention.
Silver electrodes are formed on the front and back surfaces of a rectangular piezoelectric ceramic plate (35 × 18 × 0.6) 1-1 and polarized in the thickness direction. As the piezoelectric material, a material having an electromechanical coupling coefficient k31 of 30% or more, a relative dielectric constant εr of 1800, and a mechanical quality factor Qm of about 1000 is used. The piezoelectric element is not limited to this shape, and the aspect ratio may be changed as necessary according to the design, or may be laminated in a plurality of layers. Glass epoxy FR-4 was used for the elastic substrate (70 × 20 × 2) 1-2 whose surfaces were metallized with copper.

Piezoelectric element 1-1 was bonded to the metallized surface at the center on the elastic substrate. The two unimorphs in pairs are bonded to the bonding surface with their polarization directions opposite to each other. Lead wires 1-3 were connected by soldering to the electrode surfaces and the metallized surface of the opposing elastic substrate. Lead wires 1-5 were connected by soldering between the inner metallized surface pair and the outer metallized surface pair via a diode bridge 1-4. The diode bridges 1-4 are fixed with epoxy on the inner surface of one side of the elastic substrate where the ceramic is not bonded.

Both end faces of two unimorphs to be paired were fixed with an epoxy adhesive via spacers (20 × 5 × 2t) 1-6. The spacer need not be particularly limited as a material, and can be made of an insulating material having a certain thickness and appropriate strength. In this embodiment, bakelite is used. Silicon rubber was injected into the gap in the center of the piezoelectric unit and solidified. This completes the basics of the piezoelectric unit 1.

The spring constant K calculated from the load and displacement applied to the central part of the unit was 210,000 (N / m).
Considering the load that a person steps on, it has moderate springiness and can be displaced sufficiently. According to the experiment, a voltage output of 100V to 200V was confirmed by human load.

As shown in FIG. 4, silicon rubber 2-2 is placed between copper frames 2-1 having an outer shape of 220 mm in length, 110 mm in width, and 5 mm in height, and three horizontal bars formed in a lattice at equal intervals inside. A base 2 filled to the same thickness was prepared. Ten power generation units 1 prepared in this example were arranged on this base as shown in FIG.
The lattice frame of the base is orthogonal to the longitudinal axis of each unit, is directly below the center portion, and is in electrical contact with the lower electrode of each unit. The upper surface was covered with a copper foil having a length of 220 mm, a width of 110 mm and a thickness of 50 μm, and a raw rubber plate having a length of 220 mm, a width of 110 mm and a thickness of 5 mm was placed thereon. The copper foil connected to the upper electrode of each unit in parallel, and used as an electric output terminal between the copper frame to form a piezoelectric power generation mat.
When the mat is stepped on in this configuration, the load is almost added to the average, but it was confirmed that each unit was deformed into a substantially concave lens shape, and the output current became 10 times or more due to the effect of parallel connection.

Furthermore, using the dummy structure 3 made of Bakelite at the second stage in the above-described mat structure, five pieces at the second stage are shifted by half the length, and 10 at the same position as the first stage at the third stage. The unit 1 was arranged and the upper surface was covered with a copper foil, and a raw rubber plate was further placed thereon. This configuration is schematically shown in FIG. In this case, as in the case of the battery, serial connection can be made in the thickness direction, so that the output voltage when the mat is stepped on is almost tripled, confirming the effect of overlapping.

Industrial applicability

In addition to being able to be used for road marking etc. by flashing a light emitting diode with this electric power by converting pressure change when passing a person or vehicle into electric energy by incorporating it into an indoor or outdoor facility, the present invention occurs. By storing electrical energy in a capacitor, it can be used as a backup power source for signal processing systems.

Explanatory drawing of the deformation situation related to the principle of the present invention Explanatory diagram of power generation action according to the principle of the present invention The perspective view and sectional drawing of the basic composition of the power generation unit of this invention and an Example The base part perspective view of the electric power generation mat of the basic composition of the present invention and an example Drawing of power generation mat of basic configuration of the present invention and embodiment (combination of unit and base) Sectional view of the power generation mat of the basic configuration of the present invention and the embodiment (when stacked in the thickness direction)

DESCRIPTION OF SYMBOLS 1; Electric power generation unit 1-1; Piezoelectric element 1-2; Elastic board 1-3; Lead wire 1-4; Diode 1-5; Lead wire 1-6; Spacer 2; Part frame 2-2; base part deformable part 3; dummy member

Claims (5)

Two piezoelectric unimorphs with a rectangular piezoelectric ceramic plate that is shorter than the elastic plate in the length direction on one side of an elastic plate made of a rectangular insulator metallized on both sides face each other inward. The piezoelectric power generation unit is bonded to both ends in the longitudinal direction of the elastic plate through spacers made of an insulator having a constant thickness and width. The polarization directions of the piezoelectric ceramics for the two piezoelectric unimorphs are opposite to each other with respect to the elastic plate, and the inner metallized surfaces of the piezoelectric unimorphs facing the ceramic front electrodes are connected to each other and face the inner sides. 2. The piezoelectric power generation unit according to claim 1, wherein the two poles made of the metallized surface and the two poles made of the outer metallized surface are connected by a full-wave rectifier circuit. 3. The piezoelectric power generation unit according to claim 1, wherein an organic material such as silicon rubber or elastomer is filled in a gap between the two piezoelectric unimorphs facing each other. The power generation unit according to claim 3 is laid only on a base made of a material that is hard only at the center in the length direction and the other part is easily elastically deformed, such as rubber. Piezoelectric mat characterized by 5. The piezoelectric power generation mat according to claim 4, wherein a plurality of stages are stacked in the thickness direction while being shifted by a half length in the length direction of the power generation unit according to claim 3 and electrically connected.

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