JP5961868B2 - Vibration power generation element - Google Patents

Description

  The present invention relates to a vibration power generation element that generates electric power by converting kinetic energy of vibration into electric energy using a piezoelectric effect.

  In recent years, sensors that have both a sensing function that can be attached to animals and transmit measurement data and a wireless communication function have been developed, and the power source for the operation is small, lightweight, and has a long life. It is desirable that a small and lightweight generator can be used as a power source. As a power source for such a sensor, there is a vibration power generation element that uses the piezoelectric effect and converts vibration kinetic energy into electric energy to generate electric power.

  As described in Patent Document 1, the vibration power generation element includes a vibration member fixed in a cantilever state, a weight attached to the free end of the vibration member, and a piezoelectric element joined to the vibration member. The electric power generation is performed by converting the vibration of the vibration member generated by the energy applied to the vibration member from the outside into electric energy by the piezoelectric element.

Japanese Patent No. 3170965

  When the vibration power generation element as described above is used as a power source for a sensor or the like, it is desirable to increase the output power while maintaining a small size. In order to increase the power generation amount of the vibration power generation element, it is conceivable to increase the deformation amount of the vibration member by increasing the weight. However, it is necessary to secure a space for deformation, and there is a problem that the height of the entire device increases and the size becomes large, and there is a problem against the demand for weight reduction. It is also possible to increase the power generation amount by connecting a plurality of vibration power generation elements in series. However, there is a problem that the number of vibration power generation elements is increased and the overall size is increased.

  Accordingly, an object of the present invention is to solve the problems existing in the prior art and increase the output power obtained from the unit area of the vibration power generation element.

In order to achieve the above object, the present invention provides a vibration in which a plate-like piezoelectric vibrating body having a piezoelectric member is supported by a supporting member, and electric power is generated by the piezoelectric effect according to the deformation of the piezoelectric member accompanying the vibration of the piezoelectric vibrating body. The piezoelectric vibrating body includes a laminated structure in which an upper electrode and a lower electrode are respectively formed on upper and lower surfaces of the piezoelectric member having a rectangular plane and a plate shape, and a longitudinal direction of the piezoelectric member. Are divided into a plurality of equal parts in a direction perpendicular to the plane, and the plane is composed of a plurality of divided bodies having a rectangular shape, and at least the lower surfaces of one end parts of both ends in the longitudinal direction of the plurality of divided bodies are connected by the support members. The upper electrode of one divided body is connected to the lower electrode of the other divided body by wiring between two adjacent divided bodies, and the plurality of the plurality of adjacent divided bodies On each of the split bodies An electrode and a lower electrode are electrically connected to each other in series by the wiring, and are output from the plurality of divided bodies, respectively, with vibrations synchronized with each other using the support members of the plurality of divided bodies as fixed ends. A single AC / DC conversion circuit having at least a rectifying diode for converting AC voltage supplied in series to DC voltage, and the value of the AC voltage supplied to the AC / DC conversion circuit is It is set to a value near the threshold value of the diode.

Here, the plurality of divided bodies in the present invention are formed on a single vibration member, and the support member supports a lower surface portion of at least one end portion of both end portions in the longitudinal direction of the vibration member. The weight member may be provided in a region of the lower surface of the vibration member that is not supported by the support member.

In the present invention, the length of the vibration member in the longitudinal direction is set to be larger than the length of the plurality of divided bodies in the longitudinal direction, and one end portion of both end portions in the longitudinal direction of the vibration member. Is supported by the support member, and when the one end portion is a fixed end, the other end portion is a free end capable of vibration, and the vibration member near the other end portion of the vibration member A weight member may be provided on the lower surface of the plate.

In the present invention, the length in the longitudinal direction of the plurality of divided bodies is set to be greater than the length in the longitudinal direction of the support member, and one of the end portions in the longitudinal direction of the plurality of divided bodies is set. When the end is commonly supported by the support member and the one end is a fixed end, the other end is a free end capable of vibration, and the other end of the plurality of divided bodies A common weight member may be provided on the lower surfaces of the plurality of lower electrodes in the vicinity of the portion so that the plurality of divided bodies can vibrate synchronously.

Lever by the vibration generating element of the present invention, since it is Rukoto improve the output voltage obtained from per unit area of the piezoelectric member, it is possible to increase the while maintaining a small output power (substantial amount of power generation) .

It is a whole lineblock diagram showing the whole vibration power generation element composition by the present invention. It is a side view of the 1st example of a piezoelectric vibrating body. It is a side view of the 2nd example of a piezoelectric vibrating body. It is a perspective view which shows the piezoelectric vibrating body in which the piezoelectric member is not divided | segmented. It is a perspective view which shows the piezoelectric vibrating body by which the piezoelectric member was divided | segmented into two parts. It is a perspective view which shows the piezoelectric vibrating body by which the piezoelectric member was divided | segmented into three parts. It is explanatory drawing which shows the characteristic of the diode used by an AC / DC conversion circuit. Output from a vibration power generation element when using a piezoelectric vibrator in which the piezoelectric member is not divided, a piezoelectric vibrator in which the piezoelectric member is divided into two parts, and a piezoelectric vibrator in which the piezoelectric member is divided into three parts It is the graph which compared and showed the voltage. DC output by the vibration power generation element when using a piezoelectric vibrator in which the piezoelectric member is not divided, a piezoelectric vibrator in which the piezoelectric member is divided into two parts, and a piezoelectric vibrator in which the piezoelectric member is divided into three parts It is the graph which compared and showed electric power.

Hereinafter, a vibration power generation element according to the present invention will be described with reference to the drawings.
Initially, with reference to FIG. 1, the whole structure of the vibration electric power generation element 10 by this invention is demonstrated. The vibration power generation element 10 includes a support member 12, a plate-like piezoelectric vibrating body 14 supported by the support member 12, and an AC / DC conversion circuit (hereinafter referred to as an AC / DC conversion circuit) 16.

  The support member 12 supports the piezoelectric vibrating body 14 so as to allow the piezoelectric vibrating body 14 to vibrate when external energy is applied. As in the embodiment shown in FIG. 1, the piezoelectric vibrating body 14 can be vibrated so that one end of the piezoelectric vibrating body 14 is fixed to the support member 12 and the other end of the piezoelectric vibrating body 14 is a free end. Is preferably cantilevered by the support member 12. However, if the piezoelectric vibrator 14 is allowed to vibrate when external energy is applied, the support mechanism of the piezoelectric vibrator 14 relative to the support member 12 is not limited, and at least the piezoelectric vibrator 14 The one end part should just be supported by the supporting member. For example, both ends of the piezoelectric vibrating body 14 may be fixed to the support member 12 as long as the vibration of the piezoelectric vibrating body 14 is allowed when external energy is applied.

  The piezoelectric vibrating body 14 includes a piezoelectric member formed of a piezoelectric material that generates an electromotive force by a piezoelectric effect when deformed. When the piezoelectric vibrating body 14 vibrates, an alternating voltage is generated according to the deformation accompanying the vibration. In the embodiment shown in FIG. 1, the piezoelectric vibrator 14 has one end fixed to the support member and the other end free, as shown in detail in FIG. The vibration member 18 that is cantilevered by the support member 12, the film-like piezoelectric member 20 provided on the vibration member 18, and the upper side connected to both surfaces of the film-like piezoelectric member 20 so as to sandwich this A pair of electrodes 22 including an electrode 22a and a lower electrode 22b is configured. However, the configuration of the piezoelectric vibrating body 14 is not particularly limited as long as an AC voltage is generated according to deformation caused by vibration generated when external energy is applied. For example, as shown in FIG. 3, the piezoelectric vibrating body 14 is formed by a plate-like piezoelectric member 24 and a pair of electrodes 26 including an upper electrode 26 a and a lower electrode 26 b connected so as to sandwich the piezoelectric member 24. The piezoelectric vibrating body 14 configured as described above may be supported by the support member 12. In the embodiment shown in FIG. 1, the film-like piezoelectric member 20 sandwiched between the pair of electrodes 22 is provided only on the upper surface of the vibration member 18 supported by the support member 12. Similarly, a film-like piezoelectric member sandwiched between a pair of electrodes may be provided on the lower surface of the vibration member 18.

  As shown in FIGS. 1 to 3, the piezoelectric vibrating body 14 further includes a weight member 28 in order to increase the amplitude of vibration of the piezoelectric vibrating body 14 generated when external energy is applied. It is preferable. In the embodiment shown in FIG. 1, a weight member 28 is provided at the other end of the piezoelectric vibrating body 14 whose one end is cantilevered by the support member 12. When the piezoelectric vibrating body 14 is supported at both ends by the support member 12, the weight member 28 may be provided near the central portion in the length direction of the piezoelectric vibrating body 14. The weight member 28 can be provided at any location on the piezoelectric vibrating body 14 as long as it is at a location other than the portion where the piezoelectric vibrating body 14 is supported by the support member 12.

The AC / DC conversion circuit 16 is provided to convert an AC voltage generated by the vibration of the piezoelectric vibrating body 14 into a DC voltage suitable for use in a sensor or the like. As a typical example, a configuration using two diodes and two capacitors is shown in FIG. 1. However, if an AC voltage can be converted into a DC voltage, the AC / DC conversion circuit 16 can be converted by another configuration. Of course, it may be realized.

In the vibration power generation element 10, as shown in FIG. 1, the piezoelectric member 20 , the upper electrode 22a, and the lower electrode 22b of the piezoelectric vibration member 14 are arranged in the width direction (the support end of the piezoelectric vibration member 14). It is equally divided into a plurality of (three in FIG. 1) parts in a direction perpendicular to the direction connecting the free ends , that is, a direction perpendicular to the longitudinal direction of the piezoelectric member 20 having a rectangular shape . Split by a plurality of piezoelectric member portion (hereinafter referred to as piezoelectric member divided body.) Has a plurality of electrode portions (hereinafter divided with are connected to oscillate in synchronization with each other, the electrode divided body wherein for.) are connected in series electrical by a wiring as described below. Division of the piezoelectric member 20 and a pair of electrodes (upper electrode 22a and lower electrode 22b) is not particularly limited. For example, the piezoelectric element 20 is not divided is shown in Figure 4, the upper electrode 22a and lower electrode 22b, the piezoelectric element divided body 20, respectively, as shown in FIG. 5 by two split ', the upper electrode The divided body 22a ′ and the lower electrode divided body 22b ′ may be divided into three parts, as shown in FIG. 6, and divided into three piezoelectric members 201 to 203, upper electrode divided bodies 22a1 to 22a3, and lower electrode divided. The bodies 22b1 to 22b3 may be used.

Incidentally, to divide the piezoelectric member 20 in the width direction, when divided in the length direction of the piezoelectric member 20 (direction connecting the supported end and a free end), the deformation amount of the piezoelectric element divided body are different from each other This is to prevent it from acting like an insulator. Further, by dividing the piezoelectric member 20 in the width direction, it becomes easy to synchronize the vibration of the piezoelectric member divided body together efficiently so that it is possible to take out the power.

The plurality of piezoelectric member divided bodies are vibrated in synchronization with each other by being coupled by a coupling member formed of an insulating material. In the embodiment shown in FIGS . 1 and 6 , a pair of electrode division bodies (upper electrode division bodies 22a1 to 22a3 and lower electrode division bodies 22b1 to 22b3) are sandwiched on one vibration member 18 that is not divided. Three sets of the piezoelectric member divided bodies are provided, and the three members of the piezoelectric member divided body vibrate in synchronization with each other when the vibrating member 18 functions as a connecting member. As shown in FIG. 3, the piezoelectric vibrating body 14 constituted by a plate-like piezoelectric member 24 and a pair of electrodes 26 including an upper electrode 26a and a lower electrode 26b connected so as to sandwich the piezoelectric member 24 is provided. In the case of being divided into a plurality of parts , for example, a single weight member 28 is connected to the free ends of the plurality of piezoelectric vibrating bodies 14 that are cantilevered by the support member 12, and the weight member 28 is shared. By functioning as a connecting member, the plurality of divided piezoelectric members 24 can be vibrated in synchronization with each other.

Although the form which connects the several piezoelectric member division body in series is not specifically limited, For example, as FIG . 6 which shows FIG . 1 in detail shows , the upper side formed in the upper surface of the 1st piezoelectric member division body 201 The electrode divided body 22a1 and the lower electrode divided body 22b2 formed on the lower surface of the second piezoelectric member divided body 202 adjacent thereto are connected by wiring, and the upper side formed on the upper surface of the second piezoelectric member divided body 202. The electrode divided body 22a2 and the lower electrode divided body 22b3 formed on the lower surface of the third piezoelectric member divided body 203 adjacent thereto are connected by wiring, and the lower formed on the lower surface of the first piezoelectric member divided body 201. The side electrode divided body 22 b 1 and the upper electrode divided body 22 a 3 formed on the upper surface of the third piezoelectric member divided body 203 may be connected to both input side terminals of the AC / DC conversion circuit 16.

  Next, the operation of the vibration power generation element 10 according to the present invention will be described with reference to FIG. When external energy is applied to the vibration power generation element 10, a force is applied to the piezoelectric vibrating body 14 that is cantilevered to vibrate the piezoelectric vibrating body 14 (specifically, its free end). When the piezoelectric vibrating body 14 vibrates, the piezoelectric member 20 of the piezoelectric vibrating body 14 is deformed accordingly, and charges are generated by the piezoelectric effect. As a result, a potential difference is generated between both surfaces of the piezoelectric member 20 (upper surface and lower surface in FIG. 1), and an alternating voltage is output through the pair of electrodes 22 connected to both surfaces of the vibrating piezoelectric member 20. . The AC voltage extracted through the pair of electrodes 22 is converted into a DC voltage by the AC / DC conversion circuit 16 and output.

Here, the amount of power generation when the piezoelectric member 20 having the same area and thickness is not divided and when divided into a plurality of piezoelectric member divided bodies and connected in series will be compared. When the value of the electromotive force of the piezoelectric member 20 that is not divided is V and the value of the internal resistance is r, the maximum value P1 of the power generation amount when this is connected to the load resistance of the resistance value R is given by the following equation ( 1). Desired.
P1 = V ² / (4r) (1)
On the other hand, when equally dividing the piezoelectric member 20 to the n piezoelectric member divided body, but one per electromotive force values of the n piezoelectric member divided body does not change with V, the value of the internal resistance n That is, it becomes nr. Therefore, in the whole n piezoelectric member divided bodies connected in series, the electromotive force and the internal resistance are n times, the electromotive force value is nV, the internal resistance value is n ² r, and the amount of power generation is The maximum value Pn is obtained by the following equation (2).
^{Pn = (nV) 2/4} (n 2 r) = V 2 / (4r) (2)
In other words, the amount of power generation does not change as a whole.

  However, an AC voltage is taken out from the piezoelectric vibrating body 14, and when used as a power source for a sensor or the like, the AC voltage output from the piezoelectric vibrating body 14 is AC / DC as shown in FIG. It is converted into a DC voltage through the conversion circuit 16 and used. Therefore, looking at the voltage-current characteristics of the diode used in the AC / DC conversion circuit, as shown in FIG. 7, when the voltage is close to the threshold voltage of the diode, for example, when the electromotive force is doubled, the current flows. The current becomes twice or more, and the loss in the AC / DC conversion circuit 16 is reduced. Accordingly, as in the case of the vibration power generation element 10 shown in FIG. 1, when the piezoelectric member 20 is equally divided into n piezoelectric member divided bodies 20a and these are connected in series, the electromotive force is not divided and On the other hand, the power consumption is increased by a factor of n, while the loss in the AC / DC conversion circuit 16 is reduced and the output power is increased.

  FIG. 8 shows vibration frequency-AC output voltage characteristics in the vibration power generation element 10.

Each vibration generating element 10, as shown in FIGS. 1 and 2, the upper surface of the vibration member 18 having one end portion to the frame-shaped supporting member 12 is provided with a weight member 28 to and the other end is fixed , those with a fixed piezoelectric member 20 sandwiched between the pair of electrodes 22, Ru der those made by MEMS micromachining techniques. As a comparative example, the case where the piezoelectric member 20 that is not divided as shown in FIG. 4 is provided (▽: IPZT in FIG. 8) is shown, and FIG. 5 shows an example according to the present invention. When the piezoelectric member 20 is divided into two piezoelectric member divided bodies 20 ′ as shown in FIG. 8 (◎: 2PZTs in FIG. 8), the piezoelectric member 20 is divided into three piezoelectric member divided bodies as shown in FIG. A case of dividing into 201 to 203 (▲: 3PZTs in FIG. 8) is shown. The AC output voltage is shown in FIG. 1 when the produced vibration power generation element 10 is set on a vibrator, vibrated at an acceleration of 5 m / s ² , and the applied vibration frequency is changed near the resonance frequency. The measurement was performed in a section indicated by “AC voltage” 30, that is, at a position before the AC / DC conversion circuit 16. Referring to FIG. 8, it can be seen that the AC output voltage is increased by dividing the piezoelectric member 20 and electrically connecting it in series as compared with the case where the piezoelectric member 20 is not divided. It can also be seen that the AC output voltage increases as the number of divisions of the piezoelectric member 20 increases. Note that the variation in the resonance frequency seen in FIG. 8 is due to the manufacturing process of the vibration power generation element 10 and is not essentially related to the present invention.

  FIG. 9 shows the load resistance-DC output power characteristics in the vibration power generation element 10.

Each vibration power generation element 10 is manufactured in the same manner as in FIG. 8 , and as a comparative example, a case where a piezoelectric member 20 that is not divided is provided (in FIG. 9, IPZT) is shown. As an example according to the present invention, when the piezoelectric member 20 is divided into two piezoelectric member divided bodies 20 ′ as shown in FIG. 5 (◎: 2PZTs in FIG. 9), the piezoelectric member 20 is shown in FIG. As shown, the case where the piezoelectric material is divided into three piezoelectric member divisions 201 to 203 (▲: 3PZTs in FIG. 9) is shown. The DC output power is shown as “DC voltage” 32 in FIG. 1 when the produced vibration power generation element 10 is set in a vibrator and vibrated, and the load resistance 34 shown in FIG. It was obtained by measuring at the section where it is, that is, at the position following the AC / DC conversion circuit 16. Referring to FIG. 9, it can be seen that the DC output power is increased by dividing the piezoelectric member 20 and electrically connecting it in series as compared with the case where the piezoelectric member 20 is not divided. . It can also be seen that the DC output power increases as the number of divisions of the piezoelectric member 20 increases.

As described above, according to the present embodiment, the laminated structure of the vibration power generation element 10 in which the upper electrode and the lower electrode are respectively formed on the upper and lower surfaces of the piezoelectric member is divided into a plurality of divided divided bodies. Of the two divided bodies, the upper electrode of one divided body is connected to the lower electrode of the other divided body by wiring so that the upper and lower electrodes of the plurality of divided bodies are wired. As a result of increasing the electromotive force of the vibration power generation element 10 by making the configuration electrically connected in series with each other , the vibration is compared with the case of using the undivided piezoelectric member 20 having the same area and the same thickness. AC output voltage of the power generating element 10 loss is reduced in the AC / DC converter circuit 16 is supplied, a large DC output power is obtained et than without dividing the piezoelectric member 20. Therefore, by dividing the piezoelectric member 20 into a plurality of piezoelectric member divided bodies and electrically connecting them in series, the effect of increasing the output DC power through the AC / DC conversion circuit 16 is greater than when not dividing. It becomes possible to play.

  The vibration power generating element 10 according to the present invention has been described above with reference to the illustrated embodiment. However, the illustrated embodiment is merely an example, and the structure of the vibration power generating element 10 according to the present invention is limited to the embodiment. It is not something. For example, in the illustrated embodiment, the piezoelectric vibrating body 14 is cantilevered by the support member 12, but if the piezoelectric member 20 is divided into a plurality of piezoelectric member divided bodies 20a, the piezoelectric vibrating body by the support member 12 is used. There is no limitation on the support structure 14, and as an example, both ends of the piezoelectric vibrating body 14 may be supported by the support member 12, and the weight member 28 may be provided in the center of the piezoelectric vibrating body 14.

  The vibration power generation element 10 of the present invention can be used as a main power source or an auxiliary power source for a wireless sensor terminal of a wireless sensor network used for, for example, tire pressure monitoring, infrastructure monitoring, animal health monitoring, and the like. .

DESCRIPTION OF SYMBOLS 10 Vibration power generation element 12 Support member 14 Piezoelectric vibrating body 16 AC / DC conversion circuit 18 Vibration member 20 , 20 ', 24 Piezoelectric member
22, 26 Pair of electrodes
22a, 26a Upper electrode
22a ', 22a1, 22a2, 22a3 Upper electrode divided body
22b, 26b Lower electrode
22b ', 22b1, 22b2, 22b3 Lower electrode divided body
28 Weight member
34 Load resistance
201, 202, 203 Piezoelectric member divided body

Claims (4)

A vibration power generating element that supports a plate-like piezoelectric vibrating body having a piezoelectric member by a support member and generates electric power by a piezoelectric effect according to deformation of the piezoelectric member accompanying vibration of the piezoelectric vibrating body,
In the piezoelectric vibrating body, a laminated structure in which an upper electrode and a lower electrode are formed on both upper and lower surfaces of the piezoelectric member having a rectangular plane and a plate shape is even in a direction perpendicular to the longitudinal direction of the piezoelectric member. The plane is composed of a plurality of divided bodies having a rectangular shape, and the lower surfaces of at least one end portions of both ends in the longitudinal direction of the plurality of divided bodies are commonly connected by the support member. Each upper electrode of the plurality of divided bodies is supported by connecting the upper electrode of one divided body to the lower electrode of the other divided body between two adjacent divided bodies by wiring. And the lower electrodes are electrically connected to each other in series by the wiring,
At least a rectifying diode that converts an AC voltage output from each of the plurality of divided bodies and supplied in series to a DC voltage in accordance with vibrations synchronized with each other with the support members of the plurality of divided bodies as fixed ends. Comprising a single AC / DC converter circuit having a configuration comprising:
The vibration power generation element according to claim 1, wherein a value of the AC voltage supplied to the AC / DC conversion circuit is set to a value near a threshold value of the diode . The plurality of divided bodies are formed on a single vibration member, and the support member supports a lower surface portion of at least one of the longitudinal ends of the vibration member, and the lower surface of the vibration member The vibration power generation element according to claim 1, wherein a weight member is provided in a region not supported by the support member . The length in the longitudinal direction of the vibration member is set to be larger than the length in the longitudinal direction of the plurality of divided bodies, and one end portion of both ends in the longitudinal direction of the vibration member is supported by the support member. And when the one end is a fixed end, the other end is a free end capable of vibration, and the weight member is a lower surface of the vibration member near the other end of the vibration member. The vibration power generation element according to claim 2, wherein the vibration power generation element is provided on the vibration generation element. The length in the longitudinal direction of the plurality of divided bodies is set to be greater than the length in the longitudinal direction of the support member, and one end portion of both ends in the longitudinal direction of the plurality of divided bodies is the support member. And the other end is a free end that can vibrate when the one end is a fixed end, and a plurality of the vicinity of the other end of the plurality of divided bodies The vibration power generating element according to claim 1, wherein a single weight member is provided in common on the lower surface of the lower electrode, and the plurality of divided bodies can be vibrated synchronously .

Images