JP2010273409A - Piezoelectric power generation unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric power generation unit which is high in reliability, has fewer connection points of wiring than a conventional one, and besides is low in height. <P>SOLUTION: In this cantilever support type of piezoelectric power generation unit, one end of a piezoelectric bimorph 20 is constituted by sandwiching an elastic plate 3 as an intermediate layer between two piezoelectric ceramic plates 1 and 2 and sticking them together and is fixed to a fixing part for support to perform power generation by an external force added to the piezoelectric bimorph 20. A block 5 for fixation is fixed to one end of the elastic plate 3, and the block 5 is screwed to a glass epoxy circuit board 22 being the fixing part. A land 6 plated with solder is created on the glass epoxy circuit board 22 under the block 5, and an electric connection can be made by fixation of the piezoelectric power generation unit 20. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a piezoelectric power generation unit that generates electric power using electrical energy generated when a piezoelectric material is deformed or vibrated by an external force.

  Attempts have been made to use electrical energy generated when a piezoelectric material is distorted. A piezoelectric power generation unit that generates power using such a piezoelectric element acts as a power generation device as long as the piezoelectric material has mechanical inputs such as deformation and vibration, so the generated power can be directly used or a capacitor, a secondary battery, etc. It can be stocked and used as needed. The present invention can be applied to various uses such as causing a light emitting diode to emit light without supplying power from a battery or operating a transmitter.

  Normally, when generating electricity with such a piezoelectric element, 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. Thus, the piezoelectric element is distorted to generate electric power. As the piezoelectric element, a piezoelectric bimorph configured by sandwiching an elastic body between two piezoelectric plates is generally used.

  In Patent Document 1, a piezoelectric bimorph is supported and fixed on one side of a fan, a light emitting body or music box IC is attached to the face of the fan, and power is generated by deformation of the face when the fan is looked up. A fan that emits light from the body and sounds a music box is disclosed. Patent Document 2 discloses an apparatus that generates electricity by fixing a piezoelectric bimorph with a single beam and applying a force to the opposite end. In such an application, as a method of fixing a piezoelectric bimorph supported at one end, a method of fixing by a single rod beam is common.

  On the other hand, in Patent Document 3, one end of an outer piezoelectric plate constituting a piezoelectric bimorph is directly fixed on a substrate and cantilevered, and a recess is provided in a substrate where a piezoelectric element on the free end side is displaced. There has been disclosed a piezoelectric power generation device configured to create a relief so that the tip of a displaced piezoelectric bimorph does not contact.

JP-A-8-56728 Japanese Patent Laid-Open No. 9-182465 JP-A-7-107752

  However, the method of indicating one end of the bimorph with a cantilever beam as in Patent Document 2 has a problem that the thickness of the fixed portion of the cantilever beam is increased. Further, the method of Patent Document 3 also has a problem that since the substrate portion to be attached needs to be thickened, the thickness of the power generation device becomes thick and there is a restriction in installation. Also, in any of the conventional cases, when a piezoelectric bimorph is fixed at one end and a force is applied to the opposite end, the force concentrates on the fixed end of the piezoelectric bimorph. There was a problem that crack fracture was likely to occur. In addition, in the piezoelectric bimorph configuration, it is necessary to connect the surface of the two piezoelectric elements and the three terminals of the elastic plate, so that the number of wiring connection points increases, so that the wiring is disconnected when mechanical force is applied. There was a problem that damage was likely to occur.

  Accordingly, an object of the present invention is to provide a piezoelectric power generation unit that has fewer wiring connection portions, has higher wiring reliability, and has a low profile.

  In order to solve the above-mentioned problems, a piezoelectric power generation unit according to the present invention is supported by fixing one end of a piezoelectric bimorph formed by sandwiching an elastic plate between two piezoelectric plates and fixing the fixed portion to a fixed portion. A cantilever-type piezoelectric power generation unit that generates power by external force, wherein one end of the elastic plate is fixed to the fixing portion.

  Here, the elastic plate and the fixing block may be made of a conductor, and the electrical connection between the elastic plate and the fixing portion may be obtained simultaneously with fixing the block to the fixing portion.

  The fixing portion may be a circuit board, and the block may be fixed on an electrode pad of the circuit board. Further, a screw hole is provided in a surface fixed to the fixing portion of the block, and the block May be screwed to the fixing part.

  As described above, the piezoelectric power generation unit according to the present invention directly fixes the fixed end side of the elastic plate, which is an intermediate layer of the piezoelectric bimorph, or fixes the fixing block to the fixed end side of the elastic plate. A low-profile piezoelectric power generation unit is obtained by fixing the block to the fixing part. The elastic plate and the fixing block are made of a conductor such as brass or phosphor bronze, and this part is formed on the circuit board. By fixing on the land portion of the wiring, that is, on the electrode pad, highly reliable electrical connection can be obtained without increasing the wiring. As described above, according to the present invention, it is possible to obtain a piezoelectric power generation unit that has fewer wiring connection portions than the conventional one, has high wiring reliability, and has a low profile.

The side view which shows one embodiment of the piezoelectric power generation unit by this invention. The perspective view which shows one embodiment of the piezoelectric power generation unit by this invention. It is a schematic diagram which shows the example of the electrical connection method of a piezoelectric bimorph, Fig.3 (a) is a parallel connection and FIG.3 (b) is a figure which shows a series connection. The perspective view which shows an example of the fixing method of the piezoelectric power generation unit of this Embodiment, and an electrical connection method. Sectional drawing of the piezoelectric power generation unit (this example) of this Embodiment fixed to the fixing | fixed part. Sectional drawing of the conventional piezoelectric generating unit (comparative example) fixed to the fixing | fixed part with the single beam. The figure which shows the voltage output waveform of the piezoelectric generating unit of a present Example and a comparative example. The figure which shows the durability test result of the piezoelectric generating unit of a present Example and a comparative example.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing an embodiment of a piezoelectric power generation unit according to the present invention, and FIG. 2 is a perspective view. As shown in FIG. 1, the piezoelectric unit of the present invention has a piezoelectric bimorph consisting of plate-shaped piezoelectric ceramic plates 1, 2 and an elastic plate 3 sandwiched between them, and one end of a piezoelectric bimorph interposed through a block 5. And supported by the fixed plate 21.

  Further, in the present embodiment, as shown in FIG. 2, screw holes 4 are provided in the surface fixed to the fixing plate 21 of the block 5 so that the block 5 is screwed to the fixing plate 21.

  Here, in addition to the conductor such as the metal plate as described above, various materials such as a glass epoxy substrate, a carbon fiber material, and a glass fiber material can be used as the elastic plate 3. In the normal electrical connection method of a piezoelectric bimorph, the electrode on the side bonded to the elastic plate of one piezoelectric ceramic plate is connected to the electrode on the side bonded to the elastic plate of the other piezoelectric ceramic plate. Often to do. When the elastic body is made of a conductor such as a metal plate, the inner electrodes bonded to the elastic plates of the two piezoelectric ceramic plates can be electrically connected by bonding with conductive attaching means. However, when an insulator such as a glass epoxy substrate is used as the elastic plate, electrode patterns are formed on both sides of the elastic plate, and the surface electrode of the piezoelectric ceramic plate is brought into contact with this portion to be bonded and fixed. It is necessary to take out the pattern up to the fixed end portion of the elastic plate and take out the electrode at a portion other than the adhesive surface with the piezoelectric ceramic plate to establish conduction. When an electrical connection is obtained from an electrode with an electric wire or the like, a method of performing soldering or the like is common, but it can be taken out using a conductive paste or the like.

  FIG. 3 is a schematic diagram illustrating an example of an electrical connection method of piezoelectric bimorphs. As shown in FIG. 3A, the parallel connection for short-circuiting the respective surface electrodes of the piezoelectric ceramic plate 1 and the piezoelectric ceramic plate 2 and taking out the output with the elastic plate 3, and as shown in FIG. 3B In addition, there is a series connection in which an output is extracted between the surface electrodes of the piezoelectric ceramic plate 1 and the piezoelectric ceramic plate 2. When comparing the output obtained by applying the same force to a piezoelectric bimorph of the same shape, the parallel connection has the characteristic that a high output can be obtained with a lower load resistance than the series connection, and like the piezoelectric power generation unit of this purpose The parallel connection is often used for applications in which electrical energy is extracted by applying mechanical input to the piezoelectric element.

  FIG. 4 is a perspective view showing an example of a fixing method and an electrical connection method of the piezoelectric power generation unit according to the present embodiment. FIG. 4 shows a method in which metal is used as the elastic plate 3 and the connection method is parallel connection, and the piezoelectric power generation unit 20 of the present embodiment is attached to the glass epoxy circuit board 22 as a fixing portion. The block 5 integrated with the fixed end of the elastic plate is fixed to the glass epoxy circuit board 22 with screws. A solder-plated land 6 is formed on the glass epoxy circuit board 22 facing the lower surface of the block 5, and electrical connection can be obtained simply by fixing the piezoelectric power generation unit 20 with screws. Further, the piezoelectric bimorph surface electrode is wired to the land 7 on the glass epoxy circuit board 22 by an electric wire or the like. When a force is applied to the free end of the piezoelectric power generation unit 20 in this state, a voltage is generated between the surface electrode of the piezoelectric ceramic plate and the elastic plate, and electric energy can be taken out. In FIG. 4, a rectifier circuit 8 is installed on a glass epoxy circuit board 20 and rectifies an AC attenuation type power waveform generated when a mechanical input is applied to a piezoelectric bimorph and converts it into DC power. It is possible to cause a light emitter such as an LED to emit light with this electric power, or to store it in a capacitor or a secondary battery until it reaches a certain amount, and to take it out as necessary.

  Here, in addition to the screwing method described above, the fixing method of the block 5 on the fixed end side of the elastic plate is a method of adhering with an adhesive or the like, a method of inserting the block into a slit, and the like. Is also available. Securely fixed so that it does not come off when force is applied to the free end of the piezoelectric bimorph, and electrical connection with the land or electrode terminal formed on the fixed part such as a circuit board is obtained. It only has to be done.

  Next, experimental results obtained by evaluating and comparing the characteristics and reliability of the piezoelectric power generation unit of the present embodiment and the conventional piezoelectric power generation unit are shown. 5 and 6 show the piezoelectric power generation unit used in the experiment, FIG. 5 is a cross-sectional view of the piezoelectric power generation unit of the present embodiment (hereinafter referred to as the present example) fixed to the fixed portion, and FIG. 6 shows the fixed portion. Sectional drawing of the conventional piezoelectric power generation unit (henceforth a comparative example) fixed with the single beam is shown. Each of the piezoelectric bimorphs shown in FIGS. 5 and 6 is a N10 material made by NEC TOKIN, having a length of 35 mm, a width of 10 mm, and a thickness of 0.25 mm. As the elastic plate as the intermediate layer, the brass plate 10 having a length of 41 mm, a width of 10 mm, a thickness of 0.5 mm and a fixed end extending 6 mm longer than the piezoelectric ceramic plate is used in the piezoelectric bimorph of this embodiment. In the comparative piezoelectric bimorph, a brass plate 11 having a width of 10 mm, a thickness of 0.5 mm, and a length slightly longer than 35 mm only at the solder fixing portion was used.

  In the present embodiment, the fixing method to the fixing plate 16 is such that the brass block 15 is fixed to a portion of the brass plate 10 where the fixed end side is extended, and is fixed to the fixing plate 16 with screws. In the comparative example, an acrylic prism having a length of 5 mm, a width of 6 mm, and a thickness of 6 mm is used to sandwich the piezoelectric bimorph from above and below, and the cantilever portion of the piezoelectric bimorph is sandwiched. Both sides were fixed to the fixing plate 16 with screws. The electrodes on the upper and lower surfaces of the piezoelectric bimorph are electrically connected by soldering and are short-circuited to each other.

  FIG. 7 shows voltage output waveforms of the piezoelectric power generation units of the present example and the comparative example. The piezoelectric bimorph is deformed and freely oscillated by applying an acceleration input of 1 G from the lower surface to the fixed plate 16 to which the piezoelectric bimorph is fixed at a cycle of 10 times / second, and the voltage output at this time is observed with an oscilloscope. There is almost no difference in power output between this example and the comparative example.

  Next, an experiment was carried out to confirm durability by continuously generating power from the bottom surface. FIG. 8 shows the durability test results obtained by continuously testing each of the five piezoelectric power generation units of this example and the comparative example. The horizontal axis indicates the number of power generations and the vertical axis indicates the output voltage. In the comparative example, the output decreased or exceeded the number of times exceeding 10 million times. The cause is that each time the surface of the piezoelectric ceramic plate is displaced, the external electrode on the surface of the piezoelectric ceramic plate expands and contracts, causing a crack, eventually isolating a part of the electrode and preventing conduction. The problem is that the conductive wire connected to the elastic plate is disconnected due to repeated vibration, and the output cannot be obtained. On the other hand, in this example, no decrease in output was observed even after exceeding 100 million times, and it was confirmed that the durability was improved compared to the comparative example.

  As described above, a low-profile piezoelectric power generation unit is obtained by fixing a fixing block to the fixed end of an elastic plate, which is an intermediate layer of a piezoelectric bimorph, and fixing the block to a fixed portion. By using a material such as brass or phosphor bronze as the material for the plate and the fixing block, highly reliable electrical connection can be obtained without increasing the wiring, and durability during continuous use can also be improved. .

  Needless to say, the present invention is not limited to the above-described embodiment, and the design can be changed according to the purpose and application. For example, the elastic plate can be directly fixed to a fixing portion having a structure that does not hinder the vibration of the piezoelectric bimorph without providing a block on the fixed end side of the elastic plate. The piezoelectric plate constituting the piezoelectric bimorph, the material and shape of the elastic body, and the like can be selected according to the application.

1, 2 Piezoelectric ceramic plate 3 Elastic plate
4 Screw hole 5, 15 Block 6, 7 Land 8 Rectifier circuit 10, 11 Brass plate 16, 21 Fixed plate 20 Piezoelectric generator unit 22 Glass epoxy circuit board 23 Electrode

Claims (5)

  A cantilevered piezoelectric power generation unit that generates power by external force applied to the piezoelectric bimorph by fixing one end of a piezoelectric bimorph that is formed by sandwiching an elastic plate between two piezoelectric plates and bonding them together. A piezoelectric power generation unit, wherein one end of the elastic plate is fixed to the fixing portion.   A cantilevered piezoelectric power generation unit that generates power by external force applied to the piezoelectric bimorph by fixing one end of a piezoelectric bimorph that is formed by sandwiching an elastic plate between two piezoelectric plates and bonding them together. A fixing block is fixed to one end of the elastic plate, and the block is fixed to the fixing portion.   The said elastic board and the said block for fixation are comprised with a conductor, The electrical connection between the said elastic board and the said fixing | fixed part is obtained simultaneously with fixing this block to the said fixing | fixed part. Piezoelectric generator unit.   4. The piezoelectric power generation unit according to claim 3, wherein the fixing portion is a circuit board, and the block is fixed on an electrode pad of the circuit board.   5. The piezoelectric power generation unit according to claim 3, wherein a screw hole is provided in a surface fixed to the fixing portion of the block, and the block is screwed to the fixing portion.

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