JP3611840B2 - Piezoelectric device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric device including a bending displacement type piezoelectric member.
[0002]
[Prior art]
When the piezoelectric body is displaced, electricity is generated by the piezoelectric effect, so this electricity can be used directly for the operation of electrical products and electronic products, or by storing the generated electricity in batteries and capacitors, these batteries can be used. Can be used as a drive power source for electric products or the like, or as a backup power source in case of a power failure or emergency.
[0003]
For example, Japanese Patent Laying-Open No. 9-233862 (Patent Document 1) discloses a power generator used for a wristwatch. This power generator includes a plurality of vibrating pieces fixed in a cantilever shape and a radial shape at regular intervals on the inner periphery of a watch case, a rotating weight provided in the center of the watch case, and a rotating member fixed to the rotating weight. A piezoelectric layer is provided on both surfaces of the resonator element, and protrusions are provided on the outer periphery of the rotating member at predetermined intervals. Here, as disclosed in Japanese Patent Laid-Open No. 9-233862, the rotating weight has a predetermined angle (intersection of lines connecting the center of rotation and two adjacent protrusions depending on the direction of external force applied to the rotating weight. The rotation member can be rotated clockwise or counterclockwise within the range of substantially the same angle), and the rotating member moves in the same manner as the rotation weight.
[0004]
In such a power generation device, the rotating weight rotates in response to the movement of the arm, and at this time, the protrusion provided on the rotating member comes into contact with the tip (free end) of the vibrating piece so as to contact the vibrating piece and the vibrating piece. The bonded piezoelectric layer is bent. At this time, electricity due to the piezoelectric effect is generated in the piezoelectric layer, and this electricity is charged in the capacitor (or secondary battery), thereby maintaining the driving of the timepiece.
[0005]
[Patent Document 1]
JP-A-9-233862 (pages 8-12, FIGS. 9, 16)
[0006]
[Problems to be solved by the invention]
However, in this power generator, when the protrusion provided on the rotating member comes into contact with the vibrating piece and bends the vibrating piece, the vicinity of the fixed end of the vibrating piece (that is, the vicinity of the portion attached to the watch case) ) Concentrates the stress to bend the resonator element. As a result, when the resonator element is bent repeatedly, the resonator element may be broken by the stress concentration point.
[0007]
In addition, the protrusion provided on the rotating member comes into contact with the tip of the vibrating piece and tries to bend the vibrating piece. However, stress concentrates near the fixed end of the vibrating piece, and it is easy to bend at this portion. Since the piezoelectric layer has appropriate rigidity, the resonator element is difficult to bend uniformly. In this case, since the stress is applied only to a part of the piezoelectric layer, the power generation efficiency is lowered.
[0008]
The present invention has been made in view of such circumstances, and includes a bending displacement type piezoelectric member, which suppresses local stress concentration on the piezoelectric member when the piezoelectric member is bent by an external force. An object of the present invention is to provide a piezoelectric device having excellent properties. Another object of the present invention is to provide a piezoelectric device with high power generation efficiency.
[0009]
[Means for Solving the Problems]
According to the present invention, a substantially rectangular plate-shaped piezoelectric member;
Holding means for holding one end in the longitudinal direction of the piezoelectric member or a substantially central portion in the longitudinal direction of the piezoelectric member;
A guide having a curved surface that is disposed on the side where the piezoelectric member bends when a force that bends the piezoelectric member is applied to the piezoelectric member, and that deforms the entire piezoelectric member into an arc shape in contact with the main surface of the piezoelectric member. Members,
There is provided a piezoelectric device characterized by comprising:
[0010]
According to the present invention, a substantially rectangular plate-shaped piezoelectric member;
Holding means for holding one end in the longitudinal direction of the piezoelectric member or a substantially central portion in the longitudinal direction of the piezoelectric member;
A plurality of support bars arranged on the side where the piezoelectric member bends when a force for bending the piezoelectric member is applied to the piezoelectric member, and deforms the entire piezoelectric member into an arc shape in contact with the main surface of the piezoelectric member When,
There is provided a piezoelectric device characterized by comprising:
[0011]
In such a piezoelectric device, the guide member and the support rod also have a function of restricting the maximum bending amplitude of the piezoelectric member to be constant. The piezoelectric member is a single piezoelectric element composed of piezoelectric ceramics and electrodes (a so-called monomorph element), or such a piezoelectric element and a reinforcing plate made of one or more of a metal plate and a resin plate. Those having a combined structure (so-called unimorph elements or bimorph elements) are preferably used. These piezoelectric elements may have a structure in which piezoelectric ceramics and electrodes are alternately stacked.
[0012]
According to such an apparatus, when an external force that bends the piezoelectric member is applied to the piezoelectric member, stress concentration near the holding means is less likely to occur in the piezoelectric member due to the guide member or the plurality of support rods . The durability of the member is improved. Further, since the entire piezoelectric member is bent in an arc shape so that the piezoelectric member is uniformly stressed by the guide member or the plurality of support rods , the power generation efficiency is improved. Further, since the displacement amount of the piezoelectric member is limited by the guide member or the plurality of support rods , excessive stress is not generated in the piezoelectric member, thereby extending the life of the piezoelectric member.
[0013]
The piezoelectric device of the present invention can be used as a power generation device by further comprising current collecting means for extracting electricity generated when the piezoelectric member is bent. In such a power generation device, the piezoelectric member efficiently generates electric power due to an external force applied to the piezoelectric member, and the displacement amount of the piezoelectric member is limited by the guide member or the plurality of support rods , so that an excessive voltage is applied to the piezoelectric member. Will not occur. As a result, a circuit for extracting electricity from the piezoelectric member can be configured at low cost.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of the piezoelectric device of the present invention. FIG. 1 (a) shows a state where no external force is applied to the unimorph element 11, and FIG. The state in which the external force which bends the unimorph element 11 is acting is shown. The piezoelectric device 1 includes a substantially rectangular plate-shaped unimorph element 11, a holding member 12 that holds one end in the longitudinal direction of the unimorph element 11, and a force that bends the unimorph element 11 to the unimorph element 11. And a guide member 13 that deforms the whole into an arc shape .
[0015]
As is generally known, the unimorph element 11 includes a piezoelectric element 15 having electrodes (not shown) formed on the front and back surfaces of a rectangular piezoelectric ceramic plate polarized in the thickness direction, and a reinforcing plate 16. It has a structure bonded with an adhesive. Further, as the reinforcing plate 16, a thin metal plate or a flexible printed circuit board in which a flexible resin substrate and a metal foil are bonded together is preferably used. Usually, the electrode provided on the back surface (reinforcing plate 16 side) of the piezoelectric element 15 is electrically connected to the reinforcing plate 16 (when a flexible printed wiring board is used as the reinforcing plate 16, it is electrically connected to the metal foil). Therefore, the lead wires 17 a and 17 b that collect current from the unimorph element 11 are respectively attached to an electrode (not shown) provided on the surface of the piezoelectric element 15 and the reinforcing plate 16.
[0016]
The holding member 12 holds the longitudinal end portion of the reinforcing plate 16 constituting the unimorph element 11. As the holding member 12, various hard insulating materials such as a hard resin material and a ceramic material are suitably used. When the reinforcing plate 16 is used as the ground electrode, a metal material such as aluminum or stainless steel can be used as the holding member 12. In this case, the lead wire 17 b for collecting current is replaced with the reinforcing plate 16. It can be attached to the holding member 12.
[0017]
As shown in FIG. 1, it is assumed that a downward external force A acts on the unimorph element 11 and thereby the unimorph element 11 bends downward. In the unimorph element 11, since the piezoelectric element 15 is disposed on the lower side (bending side), when the unimorph element 11 is bent downward, the piezoelectric element 15 is subjected to compressive stress. Since the piezoelectric element 15 is generally weak against tensile stress but strong against compressive stress, the durability of the unimorph element 11 is maintained long by disposing the piezoelectric element 15 on the lower side.
[0018]
The guide member 13 is disposed on the side where the unimorph element 11 is bent, that is, on the lower side of the unimorph element 11. The surface of the guide member 13 on the unimorph element 11 side is, for example, a smooth curved surface having a predetermined curvature, and when the unimorph element 11 is bent by the external force A acting on the unimorph element 11, the unimorph element 11. The main surface (the surface of the piezoelectric element 15) and the curved surface of the guide member 13 are in contact with each other, whereby the unimorph element 11 bends in a shape along the curved surface of the guide member 13. At this time, the maximum bending amplitude of the unimorph element 11 is limited to a constant value.
[0019]
For the guide member 13, similarly to the holding member 12, a hard insulating material such as a hard resin material or a ceramic material is preferably used. As shown in FIG. 1, the surface electrode of the piezoelectric element 15 constituting the unimorph element 11 is in contact with the guide member 13. Here, when the reinforcing plate 16 is used as a ground electrode, an insulating material is used for the guide member 13 because the potential of the surface electrode of the piezoelectric element 15 changes when the unimorph element 11 is bent. If an insulating means (for example, an insulating film or an insulating protrusion) is provided on the curved surface of the guide member 13, a metal material can be used for the base material of the guide member 13. On the other hand, when the surface electrode of the piezoelectric element 15 is used as a ground electrode, a metal material can be used for the guide member 13.
[0020]
FIG. 2 is an explanatory view schematically showing the bending state of the unimorph element 11 in each case where the guide member 13 is disposed and in the case where the guide member 13 is not disposed. A dotted line R in FIG. 2 shows the bending state of the unimorph element 11 when the guide member 13 is not disposed, and the vicinity of the holding member 12 is caused by the rigidity of the unimorph element 11 itself. The unimorph element 11 is bent with a large force applied to this portion. In this case, the bending of the piezoelectric element 15 (not shown) itself is small.
[0021]
On the other hand, the solid line S in FIG. 2 shows the bending state of the unimorph element 11 when the guide member 13 is arranged, and the amount of displacement of the tip of the unimorph element 11 is the same as that without the guide member 13. However, the unimorph element 11 is bent along the curved surface shape of the guide member 13, and for this reason, the piezoelectric element 15 (not shown) is also bent uniformly.
[0022]
As described above, by arranging the guide member 13, stress concentration in the vicinity of the holding member 12 is alleviated, so that the element life of the unimorph element 11 is extended. In addition, the piezoelectric element 15 is bent uniformly, and the power generation efficiency is improved. Further, when the guide member 13 is not disposed, excessive bending (that is, refraction of the unimorph element 11) in the vicinity of the holding member 12 does not return to the original position (horizontal position) by removing the external force A. in raw Ji Although some Rukoto, since the guide member 13 has a function of limiting the bending maximum displacement of the unimorph element 11, it is possible to avoid the refraction of unimorph element 11.
[0023]
The guide member 13 is not limited to the form shown in FIG. For example, as shown in FIG. 3, when a plurality of support bars 14 that are in contact with the unimorph element 11 at a predetermined position are arranged on the side where the unimorph element 11 is bent, these support bars 14 function in the same manner as the guide member 13. Generally, since the unimorph element 11 is mounted on a circuit board or held and held in a case, the support bar 14 may be held on the circuit board or case, and may be integrated with the circuit board or case. It can also be formed.
[0024]
FIG. 4 is a schematic cross-sectional view showing another embodiment of the piezoelectric device of the present invention and a schematic configuration diagram of a power generator using this piezoelectric device. The piezoelectric device 1a includes guide members 13 and 13a having substantially the same shape and arranged with the unimorph element 11 interposed therebetween. When an external force acts on the unimorph element 11 and the unimorph element 11 bends toward the guide member 13 and then the external force that has bent the unimorph element 11 is removed, the unimorph element 11 is guided by the spring property of the unimorph element 11 itself. Bends to the side, and then performs free up and down vibrations. Similar to the guide member 13, the guide member 13a controls the bending shape of the unimorph element 11 so that stress concentration does not occur in the vicinity of the holding member 12 when the unimorph element 11 bends toward the guide member 13a. The power generation efficiency of the piezoelectric element 15 is increased.
[0025]
The guide member 13 is in contact with an electrode provided on the surface of the piezoelectric element 15. When the electrode on the back surface side of the piezoelectric element 15 is used as the ground electrode, the potential of the electrode on the front surface side of the piezoelectric element 15 changes when the unimorph element 11 is bent, so that the current is collected through the lead wire 17a for current collection. Therefore, an insulating material is used as the guide member 13. Note that a metal material may be used for the base material of the guide member 13 and an insulating coating or the like may be provided on the surface thereof.
[0026]
Thus, since the voltage generated when the unimorph element 11 freely vibrates up and down is an alternating voltage, the power generation device 20 has a rectifier circuit 21 and a secondary battery 22 in order to take out and store this electricity. ing. Specifically, the rectifier circuit 21 includes a bridge circuit and a voltage regulator, converts an AC electrical signal output from the unimorph element 11 into a DC electrical signal, and further performs a peak cut of the voltage to recharge the secondary battery. Do not send an unacceptable voltage to 22. Electricity (direct current) thus obtained is charged in the secondary battery 22.
[0027]
A capacitor may be used in place of the secondary battery 22, and electricity (direct current) obtained through the rectifier circuit 21 may be directly used for driving various electronic devices. Further, by controlling the amount of displacement of the unimorph element 11 by the guide members 13 and 13a and controlling the electromotive force generated in the piezoelectric element 15, the rectifier circuit 21 may be configured without the need for a voltage regulator. it can.
[0028]
In such a power generation apparatus 20, the unimorph element 11 efficiently generates electric power by the external force applied to the unimorph element 11, and the displacement amount of the unimorph element 11 is limited by the guide members 13 and 13a. An excessive voltage is not generated. As a result, a rectifier circuit for extracting electricity from the unimorph element 11 can be configured at low cost.
[0029]
FIG. 5 is a schematic cross-sectional view showing another embodiment of the piezoelectric device of the present invention, which is an example of an embodiment when external forces A1 and A2 act on both ends of the unimorph element 11. FIG. 5A shows a state where no external force is applied to the unimorph element 11, and FIG. 5B shows a state where the external force A1 and A2 are applied to the unimorph element 11. FIG.
[0030]
The piezoelectric device 1 b includes a holding member 12 a that holds the unimorph element 11 at the center thereof, and a guide member 13 b that controls the bent shape of the unimorph element 11. The guide member 13b can be used when the external forces A1 and A2 act on the unimorph element 11 at substantially the same timing. Since the shape and function of the guide member 13b are the same as those of the guide member 13 described above, detailed description thereof is omitted here.
[0031]
As mentioned above, although embodiment of this invention has been described, this invention is not limited to such a form. For example, the piezoelectric device of the present invention is not applied only to a power generation device. When an external force acts on the unimorph element 11 and the unimorph element 11 bends, a voltage corresponding to the amount of displacement is generated in the piezoelectric element 15. Therefore, by detecting the voltage generated by the piezoelectric element 15, A sensor that measures the magnitude of the applied force or a sensor that detects the amount of displacement of the unimorph element 11 can be configured.
[0032]
When an external force that freely vibrates the unimorph element 11 acts on the unimorph element 11, for example, a force that operates a push-on / push-off type switch or a force that opens and closes various doors acts on the unimorph element 11. By doing so, it is possible to detect the on / off operation and the opening / closing operation by detecting the AC voltage generated in the piezoelectric element 15.
[0033]
In the above description, the unimorph element 11 is taken up as a piezoelectric member. However, the piezoelectric member is a monomorph element 27 in which electrodes 26 are formed on the front and back surfaces of a rectangular piezoelectric ceramic plate 25 as shown in the sectional view of FIG. There may be. Alternatively, a bimorph element 18 in which piezoelectric elements 15 (electrodes not shown) are attached to both surfaces of the reinforcing plate 16 may be used. Further, the piezoelectric element 15 may have a laminated structure in which electrodes and piezoelectric ceramic thin plates are alternately laminated. When the unimorph element 11 is used as the piezoelectric member, the piezoelectric element 15 does not always have to be arranged on the bending side, and the unimorph element is arranged so that the reinforcing plate 16 is arranged on the bending side as long as durability is ensured. 11 may be held by the holding member 12.
[0034]
【The invention's effect】
As described above, according to the present invention, when an external force that bends the piezoelectric member acts on the piezoelectric member, stress concentration near the holding means is less likely to occur on the piezoelectric member due to the guide member or the plurality of support rods . The durability of the piezoelectric member is improved. In addition, since the piezoelectric member is bent so that stress is uniformly applied to the piezoelectric member by the guide member or the plurality of support rods , the power generation efficiency is improved. Further, since the displacement amount of the piezoelectric member is limited by the guide member or the plurality of support rods , excessive stress is not generated in the piezoelectric member, thereby extending the life of the piezoelectric member. Furthermore, in the piezoelectric device of the present invention, the piezoelectric member efficiently generates electric power due to the external force applied to the piezoelectric member, and the displacement amount of the piezoelectric member is limited by the guide member or the plurality of support rods . No voltage is generated. As a result, a circuit for extracting electricity from the piezoelectric member can be configured at low cost.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an embodiment of a piezoelectric device of the present invention.
FIG. 2 is an explanatory view schematically showing a difference in bending form of a unimorph element when a guide member is arranged and when a guide member is not arranged.
FIG. 3 is a schematic cross-sectional view showing another embodiment of the piezoelectric device of the present invention.
FIG. 4 is a schematic cross-sectional view showing still another embodiment of the piezoelectric device of the present invention, and a schematic configuration diagram of a power generation device using the piezoelectric device.
FIG. 5 is a schematic sectional view showing still another embodiment of the piezoelectric device of the present invention.
FIG. 6 is a cross-sectional view showing another embodiment of a piezoelectric member used in the piezoelectric device of the present invention.
[Explanation of symbols]
Piezoelectric device 11; Unimorph element 12, 12a; Holding member 13, 13a, 13b; Guide member 14; Support rod 15; Piezo element 16; Reinforcing plate 17a, 17b; Lead wire 18; Power generation device 21; Rectifier circuit 22; Secondary battery 25; Piezoelectric ceramic plate 26; Electrode 27; Monomorph element

Claims (4)

A substantially rectangular plate-shaped piezoelectric member;
Holding means for holding one end in the longitudinal direction of the piezoelectric member or a substantially central portion in the longitudinal direction of the piezoelectric member;
A guide having a curved surface that is disposed on the side where the piezoelectric member bends when a force that bends the piezoelectric member is applied to the piezoelectric member, and that deforms the entire piezoelectric member into an arc shape in contact with the main surface of the piezoelectric member. Members,
A piezoelectric device comprising: A substantially rectangular plate-shaped piezoelectric member;
Holding means for holding one end in the longitudinal direction of the piezoelectric member or a substantially central portion in the longitudinal direction of the piezoelectric member;
A plurality of support bars that are arranged on the side where the piezoelectric member bends when a force for bending the piezoelectric member acts on the piezoelectric member and deforms the entire piezoelectric member into an arc shape in contact with the main surface of the piezoelectric member When,
A piezoelectric device comprising: The piezoelectric member is a piezoelectric element composed of piezoelectric ceramics and an electrode, or an element in which the piezoelectric element is bonded to a reinforcing plate made of one or more of a metal plate and a resin plate. The piezoelectric device according to claim 1 or 2 . The piezoelectric device according to any one of claims 1 to 3, wherein the further comprising a collector means for taking out electricity generated in the piezoelectric member in the piezoelectric member is bent.

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