JP2012200077A - Piezoelectric generator and electronic apparatus provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric generator capable of efficiently converting mechanical energy applied in a direction intersecting with a direction in which piezoelectric plates undergo deflections into electrical energy.SOLUTION: A piezoelectric generator 100 is a piezoelectric generator that converts mechanical energy applied from an outside into electrical energy. The piezoelectric generator 100 comprises: a supporting section 10; a plurality of elastic members 21 of which one end portions are fixed to the supporting section 10; piezoelectric plates 22 that are bonded with the plurality of elastic members 21 and have electrodes on front and rear surfaces; an elastic coupling member 30 for coupling the other end portions of the plurality of elastic members 21 to each other; and a weight 40 formed at a substantially center portion of the elastic coupling member 30. Since the mechanical energy applied in an unspecified direction is transmitted such that the piezoelectric plates 22 undergo flexural vibration due to movement of the weight 40, the piezoelectric generator 100 can more efficiently convert the mechanical energy into the electrical energy.

Description

  The present invention relates to a piezoelectric power generator and an electronic apparatus including the piezoelectric power generator.

  Conventionally, for example, as described in Patent Document 1, a piezoelectric plate is attached to a cantilever plate, and the piezoelectric plate is expanded and contracted by bending the plate by vibration. There has been known a piezoelectric power generation device that generates an alternating voltage.

JP-A-7-107752

  However, in the piezoelectric power generation device described in Patent Document 1, by vibrating the plate, the piezoelectric plate attached to the plate is expanded and contracted to convert it into electric energy. Is limited to energy components in the same direction. That is, only the energy component in the same direction as the bending direction of the plate out of the mechanical energy applied in the direction intersecting with the bending direction of the plate can deflect the plate, so the direction of the mechanical energy is not fixed. However, in an environment where vibration is applied from various directions, there is a problem that the conversion efficiency to electric energy is low.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 A piezoelectric power generation apparatus that converts vibration into electric energy, the first elastic member that can be repeatedly deformed by vibration, the second elastic member that can be repeatedly deformed by vibration, and the first elasticity A support portion that supports one end portion of the member and one end portion of the second elastic member, a first piezoelectric plate provided on one surface of the first elastic member, and the second A second piezoelectric plate provided on one surface of the elastic member, the other end of the first elastic member and the other end of the second elastic member are connected, and can be repeatedly deformed by vibration. An elastic connecting member and a weight provided in the elastic connecting member are provided.

  According to this application example, the first and second piezoelectric plates expand and contract by deforming the first and second elastic members, and the first and second piezoelectric plates generate electrical energy. The mechanical energy applied to the weight is transmitted to the first and second elastic members through the elastic connecting member, and deforms the first and second elastic members. At this time, the mechanical energy applied to the weight in an unspecified direction is transmitted to the first and second elastic members by continuously moving the weight, and the first and second vibrations from various directions are also transmitted to the first and second elastic members. Since the second elastic member can be deformed, it can be more efficiently converted into electric energy.

  Specifically, when the mechanical energy is applied by vibration, the weight provided in the elastic connecting member continues to move due to the elastic action of the elastic connecting member for a certain period. Even if the direction of the mechanical energy applied to the weight is a direction that intersects the deformation direction of the first and second elastic members, the kinetic energy is transmitted through the elastic connecting member during the period during which the weight moves. , Transmitted to the first and second elastic members. That is, the weight continues to transmit energy as an energy component in the deformation direction of the first and second elastic members connected by the elastic connecting member while reciprocating or circularly moving or a combination thereof. Reduce the movement. Except for energy loss such as air resistance, friction, and mechanical energy leaking outside from the support part, most of the mechanical energy of the weight is the first and second throughout the decay period during which the weight is damped. It is repeatedly transmitted as an energy component in the deformation direction of the elastic member. For this reason, the 1st piezoelectric board with which the 1st elastic member is provided, and the 2nd piezoelectric board with which the 2nd elastic member is provided can repeat expansion and contraction, and can perform energy conversion more efficiently.

  Application Example 2 In the piezoelectric power generation device according to the application example described above, the elastic modulus of the first and second elastic members is larger than the elastic modulus of the elastic coupling member.

  According to this application example, since the elastic modulus is generally a physical property value indicating difficulty of deformation, the deformation amount of the first and second elastic members with respect to external vibration is smaller than that of the elastic coupling member. . Therefore, the vibration applied from the support portion through the first and second elastic members is easily transmitted to the elastic connecting member and the weight. That is, mechanical energy can be more efficiently transmitted to the elastic connecting member including the weight.

  Application Example 3 In the piezoelectric power generation device according to the application example, one end portion of the first elastic member and one end portion of the second elastic member are joined and supported by the support portion. It is characterized by being.

  According to this application example, since the end portions of the first and second elastic members are joined by the support portion, the support portion can be configured more compactly. As a result, the power generator can be downsized. In addition, the piezoelectric power generating apparatus can be provided that has increased rigidity at the joint between the first and second elastic members and is not easily damaged even when subjected to large vibrations.

  Application Example 4 In the piezoelectric power generation apparatus according to the application example described above, a third piezoelectric plate provided on the other surface of the first elastic member facing the one surface, and the second elastic member, And a fourth piezoelectric plate provided on the other surface facing the one surface.

  According to this application example, since the first piezoelectric plate and the third piezoelectric plate are provided on both opposing surfaces of the first elastic member, one piezoelectric plate against the deformation of the first elastic member. The other piezoelectric plate is contracted, so that electric energy in opposite phases can be generated simultaneously. Similarly, since the second piezoelectric plate and the fourth piezoelectric plate are provided on both sides of the second elastic member facing each other, one piezoelectric plate extends with respect to the deformation of the second elastic member, and the other Each of the piezoelectric plates can be contracted to generate electric energy in opposite phases at the same time. For this reason, it is possible to generate power more efficiently.

  Application Example 5 An electronic apparatus according to this application example uses the piezoelectric power generation device described above.

  By using the above-described piezoelectric power generation device as an electronic device, it can be provided as an electronic device that does not have a power supply source as an essential component. For example, it is used in electronic devices that are worn on human bodies or animals where the direction of vibration is not fixed, or in an environment where power can be generated using vibrations (wind, waves, etc.) generated by natural energy. Ideal for electronic equipment.

1 is a schematic diagram illustrating a configuration of a piezoelectric power generation device according to Embodiment 1. FIG. (A)-(c); It is explanatory drawing which shows operation | movement of the piezoelectric electric power generating apparatus which concerns on Embodiment 1. FIG. FIG. 3 is a schematic diagram illustrating a configuration of a piezoelectric power generation device according to a second embodiment. FIG. 6 is a schematic diagram illustrating a configuration of a piezoelectric power generation device according to Modification 1. It is a circuit diagram which shows the usage example of a piezoelectric generator.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Embodiments of the invention will be described below with reference to the drawings. In the following drawings, the scale may be different from the actual scale for easy understanding.

(Embodiment 1)
FIG. 1 is a schematic diagram illustrating a configuration of a piezoelectric power generation device 100 according to the first embodiment.
The piezoelectric power generation apparatus 100 is a piezoelectric power generation apparatus using two piezoelectric elements, and includes a support portion 10, an elastic member 21, a piezoelectric element 20, an elastic connecting member 30, a weight 40, and the like.

  The support unit 10 is a substantially rectangular parallelepiped block serving as a base of the piezoelectric power generation device 100, and supports and fixes one end portion 21 b of each of the two elastic members 21. The support portion 10 receives mechanical energy from the outside, and transmits the energy to the elastic connecting member 30 and the weight 40 connected to the other end 21 t of the elastic member 21 via the elastic member 21.

The support portion 10 is made of a non-piezoelectric material, and alumina (Al ₂ O ₃ ) is used as a suitable example in this embodiment. Examples of non-piezoelectric materials include alumina, zirconia (ZrO ₂ ), silicon, silicon nitride, silicon carbide, quartz, and organic polymers.

  The piezoelectric element 20 includes a piezoelectric plate 22, an electrode plate 23, a wiring 24 and the like, and is provided in the elastic member 21. The two elastic members 21 are arranged so as to face each other and are substantially parallel to each other and extend in a substantially vertical direction with respect to the support portion 10, and each end portion 21 b is formed on the support portion 10. It is inserted and fixed. The arrangement of the two elastic members 21 is not particularly limited. If the two elastic members 21 are arranged substantially parallel to each other with a gap therebetween, the two elastic members 21 are deformed in the same manner with respect to vibration, and thus are generated from the piezoelectric plate 22. The electric energy to be equalized. Therefore, it becomes easy to predict the amount of electric energy generated by vibration.

  The piezoelectric plate 22 includes an electrode plate 23 and is attached to a portion that expands and contracts when one vibration is input to the elastic member 21. Due to the bending of the elastic member 21, one piezoelectric plate 22 is extended and the other piezoelectric plate 22 is contracted, so that each can generate electric energy in opposite phases at the same time.

  The electrode plate 23 is a metal plate having the same area as the piezoelectric plate 22, and is attached to the front and back surfaces of the piezoelectric plate 22. The electrode plate 23 leads the electrical energy generated by the piezoelectric plate 22 to the terminals A, A ′, B, B ′ through the wiring 24.

  As a suitable example, SUS (Stainless Used Steel) is used for the elastic member 21. However, the present invention is not limited to this, and ceramics such as alumina and zirconia, brass, phosphor bronze, and the like may be used.

For the piezoelectric plate 22, lead zirconate titanate (PZT) is used as a preferred example. In addition, it is not limited to this, Lead magnesium niobate (PMN) -PZT, Lead nickel niobate (PNN) -PZT, PMN-Lead titanate (PT), Barium titanate (BaTiO ₃ ), etc. Piezoelectric ceramics or piezoelectric polymers such as polyvinylidene fluoride (PVDF) may be used.
The piezoelectric plate 22 is previously polarized so that a voltage is generated in the thickness direction due to contraction in the extending direction.

  The elastic connecting member 30 connects the end portions 21 t of the two elastic members 21. That is, the free ends that are not fixed to the support portion 10 of the elastic member 21 are connected by the elastic connecting member 30.

The weight 40 is formed at a substantially central portion of the elastic connecting member 30. The kinetic energy of the weight 40 is transferred between the elastic energy of the elastic connecting member 30 and transmitted to the connected elastic member 21 through the elastic connecting member 30. By forming the weight 40 substantially at the center of the elastic connecting member 30, the two elastic members 21 are deformed in the same manner with respect to vibration, so that the electric energy generated from the piezoelectric plate 22 is also equal. Therefore, it becomes easy to predict the amount of electric energy generated by vibration.
As the weight 40, SUS is used as a preferable example. However, the present invention is not limited to this, and ceramics such as alumina and zirconia, brass, phosphor bronze, and the like may be used. In addition, a higher density (specific gravity) is preferable for a more compact configuration.

  The weight 40 may be formed so as to be provided around the substantially central portion of the elastic connecting member 30 that connects the two end portions 21t, or the weight 40 is disposed at an intermediate position between the two end portions 21t. The structure which connects the weight 40 with the edge parts 21t of both sides by the two elastic connection members 30 may be sufficient. Moreover, the structure which gives the function of the weight 40 to elastic connection member 30 itself by changing the shape of the center part of the elastic connection member 30 (thickening, making it thick etc.) may be sufficient.

For the elastic connecting member 30, a spring made of SUS is used as a preferred example. The material of the spring is not limited to this, and titanium, phosphor bronze, piano wire (carbon steel), etc. may be used. The elastic connecting member 30 is not necessarily a spring, and is an elastic body that can absorb the kinetic energy of the weight 40 including elastic material as elastic energy, and can diverge and transmit the energy to the weight 40 and the elastic member 21. I just need it.
The material, elastic modulus, length, and weight of the elastic connecting member 30 and the material, shape, weight, size, and the like of the weight 40 depend on the generation environment of mechanical energy used for power generation and the specifications of the power generation energy. It is preferable to select the optimum specification as appropriate together with the specification of the piezoelectric element 20.

  Note that the elastic modulus of the elastic member 21 is preferably equal to or greater than the elastic modulus of the elastic connecting member 30. By configuring the elastic member 21 to be harder to be deformed than the elastic connecting member 30, external stress input to the support portion 10 and applied via the elastic member 21 is transmitted to the elastic connecting member 30 more. It becomes easy to do.

According to the above configuration, when mechanical energy is applied to the support portion 10 as an external force, the elastic member 21 is flexed so as to vibrate, and the piezoelectric plate 22 expands and contracts to generate electrical energy. Specifically, the external force input to the support portion 10 is transmitted to the weight 40 via the elastic member 21 and the elastic connecting member 30. The weight 40 continues to move by repeatedly exchanging energy with the elastic energy of the elastic connecting member 30 for a certain period of time by the transmitted mechanical energy. Throughout the period in which the weight 40 moves, the kinetic energy is continuously transmitted to the elastic member 21 as an energy component in the direction of bending the elastic member 21.
A more specific operation will be described below.

  2A to 2C are explanatory views showing the operation of the piezoelectric power generation apparatus 100 according to this embodiment. In each of the drawings, the XYZ triaxial directions orthogonal to each other are the direction in which the piezoelectric element 20 extends from the end 21b (fixed end) to the end 21t (free end), and the direction connecting the ends 21t. A direction intersecting the Y direction, the Z direction, and the Y direction is defined as an X direction.

  FIG. 2A is a side view of the state in which the weight 40 receiving an external force is reciprocating in the Z direction as viewed from the X direction. As is apparent from the drawing, the end 21t connected to the weight 40 by the elastic connecting member 30 is pulled or returned by the weight 40 that reciprocates in the Z direction and reciprocates in the Y direction. The reciprocating motion of the end portion 21t is a reciprocating motion that deflects the piezoelectric element 20, and as a result, electric energy is generated in the piezoelectric plate 22.

  FIG. 2B is a top view of the state in which the weight 40 receiving an external force is reciprocating in the X direction, as viewed from the Z direction. As is apparent from the figure, the end 21t connected to the weight 40 by the elastic connecting member 30 is pulled or returned by the weight 40 that reciprocates in the X direction and reciprocates in the Y direction. The reciprocating motion of the end portion 21t is a reciprocating motion that deflects the piezoelectric element 20, and as a result, electric energy is generated in the piezoelectric plate 22.

  FIG. 2C is a side view of the state in which the weight 40 receiving an external force is reciprocating in the Y direction as viewed from the X direction. As is apparent from the drawing, the end 21t connected to the weight 40 by the elastic connecting member 30 is pushed and pulled by the weight 40 that reciprocates in the Y direction and reciprocates in the Y direction. The reciprocating motion of the end portion 21t is a reciprocating motion that deflects the piezoelectric element 20, and as a result, electric energy is generated in the piezoelectric plate 22.

  The actual movement of the weight 40 is not limited to the reciprocating movement in the single direction as described above, and the X, Y, and Z direction components are influenced by the direction in which the external force is applied and the deflection of the elastic member 21. It becomes a complicated movement in a three-dimensional space in which the movements are combined. That is, the movement is a combination of reciprocating movement, circular movement, vibration and the like. However, any movement in the three-dimensional space prompts the end portion 21t to reciprocate in the Y direction. The weight 40 attenuates its movement while transmitting energy as an energy component in a direction in which the elastic member 21 connected by the elastic connecting member 30 is bent.

As described above, according to the piezoelectric power generation device 100 according to the present embodiment, the following effects can be obtained.
Even if the direction of the mechanical energy applied to the weight 40 intersects the direction in which the elastic member 21 bends, the kinetic energy during the period in which the weight 40 moves is the energy in the direction in which the elastic member 21 is vibrated by the deflection. As a component, it is continuously transmitted to the elastic member 21. At this time, the mechanical energy applied to the weight 40 not only in the direction in which the elastic member 21 bends but also in an unspecified direction is transmitted to the elastic member 21 by the continuous movement of the weight 40, and thus more efficient. Can be converted into electrical energy.

That is, except for energy loss such as air resistance, friction, and mechanical energy leaking to the outside from the support portion 10, most of the mechanical energy of the weight 40 is repeatedly used as an energy component in the direction in which the elastic member 21 is vibrated by deflection. Communicated. For this reason, since the piezoelectric plate 22 bonded to the elastic member 21 repeatedly expands and contracts, energy conversion can be performed more efficiently.
As described above, according to the present embodiment, it is possible to provide a piezoelectric power generation apparatus that can efficiently convert mechanical energy applied in a direction intersecting with the bending direction of the piezoelectric plate 22 into electric energy.

Further, according to the present embodiment, the motion characteristics of the weight 40 can be changed by changing the weight of the weight 40 and the elastic modulus of the elastic connecting member 30. Specifically, the cycle of the circular motion and reciprocation of the weight 40 and the half-life period of the damped vibration can be adjusted, and efficient power generation can be obtained with respect to the magnitude of external vibration. The following effects can also be obtained.
By simply replacing the weight 40 and the elastic connecting member 30 with different specifications, the piezoelectric power generation apparatus can be optimized in accordance with the environment of the mechanical energy generation source used for power generation. That is, variations as a piezoelectric power generation device can be provided simply. For example, when the vibration range specific to each environment is known (periodic motion of waves, walking of people, flapping of birds, etc.), a configuration that efficiently generates power in accordance with each vibration should be set in advance. Can do.
Moreover, it can also be utilized as a sensor function for detecting and transmitting a specific vibration by utilizing the fact that the amount of power generation reaches a peak at the vibration resonance point. Even in this case, the detection range can be set in advance simply by changing the weight 40 and the elastic connecting member 30.

(Embodiment 2)
Next, the piezoelectric power generator according to Embodiment 2 will be described. In the description, the same components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

FIG. 3 is a schematic diagram illustrating a configuration of the piezoelectric power generation apparatus 200 according to the second embodiment.
The second embodiment is characterized in that one end portion 21 b of each of the two elastic members 21 facing each other is joined by the joint portion J, and the joint portion J is fixed to the support portion 10.
In the first embodiment, the two elastic members 21 have been described as being arranged so as to extend in a substantially vertical direction with respect to the support portion 10 in a substantially parallel manner with a gap therebetween, but in the present embodiment, The two end portions 21b are joined at one place by the joint portion J, and the two end portions 21t and the joint portion J form a triangle.

  According to the present embodiment, since the respective end portions 21b of the two elastic members 21 are joined to one joint portion J, the support portion 10 that fixes the joint portion J can be configured more compactly. Therefore, the generator itself can be downsized. Further, since the end portions 21b of the two elastic members 21 are joined, the rigidity of the end portions 21b is increased, and a generator that is not easily damaged even when subjected to large vibrations can be provided. Further, when the elastic member 21 bends in the opposite phase in the opposite directions or vibrates in the opposite phase, the stress cancels out at the joint portion J, so that energy leaking from the joint portion J to the support portion 10 is reduced. Thus, energy can be transmitted to the piezoelectric plate 22 more effectively. As a result, power can be generated more efficiently.

  Note that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be added to the above-described embodiment.

(Modification 1)
A piezoelectric power generator according to Modification 1 will be described below. In addition, about the component same as Embodiment 1, the same code | symbol is used and the overlapping description is abbreviate | omitted.

FIG. 4 is a schematic diagram illustrating a configuration of a piezoelectric power generation device 300 according to the first modification.
In the first and second embodiments, the piezoelectric power generation apparatus using two piezoelectric elements has been described. However, the present invention is not limited to this configuration, and may be configured by three or more piezoelectric elements.

  In the present modification, three piezoelectric elements 20 are arranged on the support portion 10 in a substantially vertical direction so that the centers thereof face each other. The support portion 10 supports and fixes one end portion 21 b of each of the three piezoelectric elements 20. The elastic connecting member 30 connects the end portions 21 t of the three elastic members 21. The weight 40 is formed at a substantially central portion of the elastic connecting member 30 that connects the three end portions 21t. The kinetic energy of the weight 40 is configured to be transferred to and from the connected elastic member 21 through the elastic connecting member 30 by repeatedly exchanging energy with the elastic energy of the elastic connecting member 30.

According to the piezoelectric power generation apparatus 300 according to this modification, in addition to the effects in the first embodiment, the following effects can be obtained.
The weight 40 is formed at a substantially central portion of the elastic connecting member 30 that connects the three end portions 21t. Since the weight 40 is supported from three directions, the movement range of the weight 40 when receiving mechanical energy. Can easily be controlled in a space surrounded by the three piezoelectric elements 20. Further, since the mechanical energy received by the weight 40 can be exchanged between the elastic energy of the elastic connecting member 30 and the three piezoelectric elements 20 in the three directions, it is larger than in the case of the first and second embodiments. Mechanical energy can be added. Therefore, it can be effectively used when generating power using natural energy having a larger acceleration.

  Further, although not shown, the end portions 21b of the three piezoelectric elements 20 may be bonded to one place at the bonding portion, and the bonding portion may be fixed to the support portion 10.

(Electronics)
Next, an electronic device using the piezoelectric power generation device of this embodiment will be described.
FIG. 5 is a circuit diagram showing a charging circuit 400 as an example using any one of the piezoelectric power generation devices 100 to 300.
The charging circuit 400 includes the piezoelectric power generation device, a bridge rectifier 50, a charging capacitor 51, a Zener diode 52, and the like.
Since the electric energy generated by the piezoelectric power generator is alternating current, it is rectified by the bridge rectifier 50 and stored in the charging capacitor 51. The Zener diode 52 is provided for overvoltage protection.

  The electrical energy stored in the charging capacity 51 can be used as a power source for the connected load 53. The charging circuit is connected to the power source of the load 53 connected to the terminals C and C ′. Various electronic devices can be connected. That is, it is possible to provide more excellent characteristics as an electronic device that can be operated without a power source such as a battery. For example, it is ideal for electronic devices that are used by attaching to human bodies and animals whose direction of movement is not fixed, and electronic devices that are used in environments that can generate power using natural energy movement (wind, waves, etc.) It is.

  DESCRIPTION OF SYMBOLS 10 ... Support part, 20 ... Piezoelectric element, 21 ... Elastic member, 21b, 21t ... End, 22 ... Piezoelectric plate, 23 ... Electrode plate, 24 ... Wiring, 30 ... Elastic coupling member, 40 ... Weight, 100, 200, 300 ... piezoelectric generator, 400 ... charge circuit.

Claims (5)

A piezoelectric generator that converts vibration into electrical energy,
A first elastic member that can be repeatedly deformed by vibration;
A second elastic member that can be repeatedly deformed by vibration;
A support portion that supports one end portion of the first elastic member and one end portion of the second elastic member;
A first piezoelectric plate provided on one surface of the first elastic member;
A second piezoelectric plate provided on one surface of the second elastic member;
An elastic connecting member that connects the other end of the first elastic member and the other end of the second elastic member, and can be repeatedly deformed by vibration;
And a weight provided on the elastic connecting member.   2. The piezoelectric power generation apparatus according to claim 1, wherein an elastic modulus of the first and second elastic members is larger than an elastic modulus of the elastic coupling member.   The one end portion of the first elastic member and the one end portion of the second elastic member are joined to each other and supported by the support portion. The piezoelectric power generation device described. A third piezoelectric plate provided on the other surface of the first elastic member facing the one surface;
A fourth piezoelectric plate provided on the other surface of the second elastic member facing the one surface;
The piezoelectric power generator according to claim 1, further comprising:   An electronic apparatus using the piezoelectric power generation device according to any one of claims 1 to 4.

Images