JP2013080768A - Power generating device, method for controlling power generating device, electronic device, and transportation means - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power generator capable of obtaining a large amount of power generation by adjusting a resonance frequency with a small circuit scale.
Displacement information which is information relating to a displacement due to deformation of the deformable member, a first piezoelectric element (108, 109a, 109b) provided on the deformable member, and the deformable member. And a resonance frequency adjusting means 119 for adjusting a resonance frequency of the deforming member based on a control signal, including a displacement detecting means 140 for generating the adjusting member and an adjusting piezoelectric element (114, 115a, 115b) provided on the deforming member. , An inductor L constituting a resonance circuit including the first piezoelectric element, a switch SW provided in the resonance circuit, the control signal is generated based on the displacement information, and the switch is generated based on the displacement information. And a control means 112 that keeps the switch in a conductive state for a predetermined period.
[Selection] Figure 1

Description

  The present invention relates to a power generation device that extracts, as electric energy, a charge generated when a piezoelectric material such as a piezoelectric element is deformed by an external force, a control method thereof, an electronic device including the power generation device, a moving unit, and the like.

  When piezoelectric materials such as lead zirconate titanate (PZT), quartz (SiO2), and zinc oxide (ZnO) are deformed, electric polarization is induced inside the material, and positive and negative charges appear on the surface. Such a phenomenon is called a so-called piezoelectric effect. A power generation method has been proposed in which the cantilever beam is vibrated by repeatedly applying a load to the piezoelectric material by utilizing such properties of the piezoelectric material, and electric charges generated on the surface of the piezoelectric material are taken out as electricity.

  For example, an alternating current is generated by providing a weight at the tip and vibrating a metal cantilever with a piezoelectric material thin plate and taking out positive and negative charges alternately generated in the piezoelectric material in accordance with the vibration. A technique has been proposed in which this alternating current is rectified by a diode, stored in a capacitor, and extracted as electric power (Patent Document 1). If this technology is used, the power generation device can be reduced in size, and therefore, for example, an application such as incorporation in a small electronic component instead of a battery is expected.

JP-A-7-107752

  However, the proposed conventional technique has a problem that the amount of power generation is reduced when it is installed in a place where an appropriate external force cannot be obtained. That is, when the vibration due to external force (hereinafter referred to as environmental vibration) does not coincide with the resonance frequency of the cantilever with the piezoelectric material thin plate attached thereto, the amount of power generation is reduced because the deformation of the piezoelectric material is small. However, the resonance frequency of a cantilever beam is often determined at the time of manufacture and shipment depending on, for example, the length, thickness, material, weight of the beam, and the like. For this reason, it is generally difficult to adjust in accordance with the environmental vibration of the installation location.

  To solve this problem, for example, a solution is conceivable in which a mechanism for mechanically adjusting the length of the beam is added to the power generation device. Further, for example, a solution of using a power generation device including a plurality of cantilever beams having different beam lengths is also conceivable. In the former case, for example, the user adjusts the resonant frequency of the cantilever at the installation location. In the latter case, it can be expected that the resonance frequency of any of the cantilevers matches the frequency of the environmental vibration. However, in any case, the size of the power generation device becomes large.

  The present invention has been made to solve the above-described problems. According to some aspects of the present invention, there is provided a power generation apparatus that uses the piezoelectric effect of a piezoelectric material, and that can generate a large amount of power generation by adjusting a resonance frequency with a small circuit scale.

(1) The present invention is a power generation device, and includes a deformation member that is deformed by switching a deformation direction, a first piezoelectric element provided on the deformation member, and displacement that is information relating to displacement due to deformation of the deformation member. A displacement detecting means for generating information; an adjustment piezoelectric element provided on the deformable member; a resonance frequency adjusting means for adjusting a resonance frequency of the deformable member based on a control signal; and the first piezoelectric element. An inductor constituting a resonance circuit including the switch, a switch provided in the resonance circuit, and a control unit that generates the control signal based on the displacement information and sets the switch in a conductive state for a predetermined period based on the displacement information; .

(2) In this power generation device, the resonance frequency adjusting means includes a variable resistor connected to a pair of electrodes of the adjusting piezoelectric element, and the resistance value of the variable resistor may be changed based on the control signal. Good.

(3) In this power generation device, the displacement detection means includes a second piezoelectric element provided in the deformable member, and a voltage detection circuit that detects a voltage generated in the second piezoelectric element, The displacement information may be generated based on the voltage detected by the voltage detection circuit.

(4) In this power generation device, the displacement detection unit includes a second piezoelectric element provided in the deformable member, and a current detection circuit that detects a current flowing from the second piezoelectric element, and the current The displacement information may be generated based on the current detected by the detection circuit.

  In these inventions, since the first piezoelectric element is provided on the deformable member, the first piezoelectric element is also deformed when the deformable member is deformed. As a result, positive and negative charges are generated in the first piezoelectric element due to the piezoelectric effect. Note that the amount of generated charge increases as the amount of deformation of the first piezoelectric element increases.

  Here, it is known that if the resonance frequency of the deformable member and the frequency of environmental vibration are the same, the deformable member vibrates greatly and a large amount of power generation can be obtained. However, the environmental vibration varies depending on the environment where the power generation apparatus is installed, and the same environmental vibration frequency as the resonance frequency of the deformable member is not always obtained. These inventions include the resonance frequency adjusting means for adjusting the resonance frequency, so that the resonance frequency of the deformable member can be adjusted in accordance with the environmental vibration.

  The resonance frequency adjusting means includes an adjustment piezoelectric element provided on the deformable member, and adjusts the resonance frequency using the piezoelectric effect or the inverse piezoelectric effect. For example, the resonance frequency adjusting means may include a variable resistor connected to the pair of electrodes of the adjusting piezoelectric element, and may change the resistance value of the variable resistor based on the control signal. For example, when the resistance value is reduced, positive and negative charges generated in the electrodes due to the piezoelectric effect are likely to flow through the variable resistance. For this reason, the electric charge generated in the electrode is reduced, so that a force acts in a direction in which the distortion of the adjusting piezoelectric element is restored. Here, since the adjustment piezoelectric element is provided on the deformable member, the deformable member is less likely to be distorted, and the resonance frequency thereof is increased. If the resonance frequency does not need to be increased, the resistance value may be set to a sufficiently large value.

  Here, the control signal input to the resonance frequency adjusting means is generated by the control means based on the displacement information. The displacement information is information regarding displacement due to deformation of the deformable member. The displacement detection means may generate displacement information by measuring, for example, the deformation of the deformable member directly, or may generate displacement information based on a signal that changes in response to the displacement of the deformable member. If the resonance frequency of the deformable member and the frequency of environmental vibration are the same, the deformable member vibrates greatly, and its amplitude reaches a peak (maximum value). For example, the control unit may first sweep the resistance value of the variable resistor according to the control signal to determine a specific resistance value at which the amplitude reaches a peak (maximum value). Then, a control signal designating a specific resistance value or voltage value may be given to the resonance frequency adjusting means.

  As described above, the power generation devices of these inventions can adjust the resonance frequency of the deformable member to greatly vibrate the deformable member in accordance with the environmental vibration, thereby obtaining a large amount of power generation. At this time, since a mechanism for adjusting the length of the beam mechanically and a plurality of cantilever beams having different lengths are not required, the size of the apparatus can be reduced.

  In these inventions, the first piezoelectric element forms a resonance circuit together with the inductor, and the resonance circuit is provided with a switch. Then, by making the switch conductive at an appropriate timing by the control means, the arrangement of positive and negative charges generated in the first piezoelectric element can be reversed, and there is no need to prepare a booster circuit separately. A high voltage can be obtained with a small circuit scale.

  Here, the control means enables efficient power generation by determining the timing at which the switch is turned on based on the displacement information. As described above, the displacement information is information relating to the displacement due to the deformation of the deformable member, and is generated by the displacement detection means. At this time, the displacement detection means may obtain the displacement information by detecting the voltage of the second piezoelectric element. Alternatively, the displacement detection means may obtain the displacement information by detecting the current of the second piezoelectric element.

  At this time, deformation of the deformable member is started in a state where the switch is disconnected, and the switch is turned on when the amount of deformation becomes an extreme value (that is, when the deformation direction is switched). The first piezoelectric element (and the second piezoelectric element) is deformed together with the deformable member, and the larger the amount of deformation, the more electric charge is generated. Therefore, the electric charge generated in the first piezoelectric element (and the second piezoelectric element) The first piezoelectric element is connected to the inductor to form a resonant circuit. Then, the electric charge generated in the first piezoelectric element flows into the inductor. Since the first piezoelectric element and the inductor constitute a resonance circuit, the current flowing into the inductor overshoots and flows into the terminal on the opposite side of the first piezoelectric element. During this period (that is, a period until the electric charge flowing out from one terminal of the first piezoelectric element flows again into the first piezoelectric element from the opposite terminal via the inductor), the first piezoelectric element and It becomes half the resonance period of the resonance circuit formed by the inductor. Therefore, when the deformation direction of the first piezoelectric element is switched, the switch is connected to form a resonance circuit, and then the inductor is connected if the switch is disconnected when half the resonance period has elapsed. The arrangement of positive and negative charges previously generated in the first piezoelectric element can be reversed. From this state, if the deformable member is deformed in the opposite direction, the first piezoelectric element is deformed in the opposite direction. Therefore, a new phenomenon generated by the piezoelectric effect from the state where the arrangement of the positive and negative charges is reversed is obtained. Charges are accumulated in the first piezoelectric element so that the charges are accumulated. Further, since the voltage generated as the electric charge is accumulated in the first piezoelectric element also increases, the voltage generated by the electric polarization of the piezoelectric material constituting the first piezoelectric element can be obtained without preparing a booster circuit separately. High voltage can be generated. Further, in order to efficiently store charges in the first piezoelectric element in this way, it is important to connect a switch to form a resonance circuit when the deformation direction of the first piezoelectric element is switched. Here, since the deformation member is provided with the first piezoelectric element and the second piezoelectric element, when the deformation direction of the first piezoelectric element is switched, the deformation direction of the second piezoelectric element is also switched. Since the second piezoelectric element also generates a higher voltage as the amount of deformation increases, the voltage generated by the second piezoelectric element is an extreme value when the deformation direction of the second piezoelectric element is switched. For this reason, for example, if the voltage generated in the second piezoelectric element is detected and the switch is turned on only for a predetermined period from the time when the voltage reaches the extreme value, the electric charge is efficiently charged in the first piezoelectric element. Can be accumulated.

(5) In this power generation device, the first piezoelectric element and the adjustment piezoelectric element may be provided on different surfaces of the deformable member.

  According to the present invention, since the first piezoelectric element and the adjusting piezoelectric element are provided on different surfaces of the deformable member, the installation area of the first piezoelectric element can be increased, and high power generation capability is ensured. Is possible. This is because if the first piezoelectric element and the adjustment piezoelectric element are provided on the same surface of the deformable member, the installation area may be reduced.

  In addition, since the installation area of the adjustment piezoelectric element can be increased, the adjustment range of the resonance frequency of the deformable member can be expanded.

(6) In this power generation device, the first piezoelectric element and the adjustment piezoelectric element may be provided on the same surface of the deformable member.

  According to the present invention, if the first piezoelectric element and the adjusting piezoelectric element are provided on the same surface of the deformable member, the first piezoelectric element and the adjusting piezoelectric element are deformed at the same time (in the same process). Can be provided. For this reason, it becomes possible to manufacture a power generator with high productivity.

  At this time, if there is a second piezoelectric element, the second piezoelectric element may be provided on a different surface of the deformable member. Since the installation area of the second piezoelectric element can be increased, the displacement detection means can increase the accuracy of the displacement information detected based on, for example, the voltage generated in the second piezoelectric element.

(7) The present invention provides a displacement detection that generates displacement information that is information related to displacement caused by deformation of the deformation member, the first piezoelectric element provided on the deformation member, and the deformation member that is deformed by switching the deformation direction. And a resonance frequency adjusting means for adjusting a resonance frequency of the deformable member based on a control signal, the control method of the power generation device comprising: an adjustment piezoelectric element provided on the deformable member; Obtaining information, and generating the control signal based on the displacement information.

  According to the present invention, in a power generation device including a resonance frequency adjusting unit that adjusts a resonance frequency based on a control signal, a control including a step of acquiring displacement information and a step of generating a control signal based on the displacement information I do. As described above, the generated control signal is a control signal that specifies a specific resistance value or the like at which the amplitude of the signal given as the displacement information peaks. At this time, by adjusting the resonance frequency of the deformable member, the deformable member is vibrated greatly in accordance with the environmental vibration, and a large amount of power generation can be obtained. Further, unlike a mechanism that mechanically adjusts the length of the beam, the resonance frequency can be automatically adjusted without requiring the user to perform adjustment work.

(8) The present invention is an electronic device including any of the power generators described above.

(9) The present invention is a moving means including any one of the power generators described above.

  These inventions are small electronic devices such as a remote controller in which the power generation device is incorporated instead of a battery, or moving means such as a vehicle or a train on which the power generation device is mounted. For example, when the electronic device is carried or used, the electronic device can generate electric power due to vibration. This electronic device does not require work such as battery replacement. In addition, the moving means (for example, a vehicle, a train, etc.) can generate electric power by vibration accompanying the movement, and can supply power to, for example, equipment provided in the moving means. Whether mounted on an electronic device or mounted on a moving means, the resonance frequency of the deformable member is adjusted in accordance with environmental vibration, so that power generation efficiency can be increased.

It is explanatory drawing which showed the structure of the electric power generating apparatus of a present Example. It is explanatory drawing about the charge in the electrical storage element of a present Example. It is explanatory drawing about the correlation of the displacement of a deformation | transformation member, and an electrical signal. It is explanatory drawing about the relationship between the amplitude of the deformation member of a present Example, and the resistance value of a variable resistance. It is explanatory drawing which showed the structure of the electric power generating apparatus of a present Example in detail. It is explanatory drawing which showed operation | movement of the electric power generating apparatus of a present Example. It is explanatory drawing which showed notionally the first half part of the operation principle of the electric power generating apparatus of a present Example. It is explanatory drawing which showed notionally the latter half part of the operation principle of the electric power generating apparatus of a present Example. It is the flowchart which showed the control processing of a present Example. It is the flowchart which showed switch control processing. It is the figure which showed the example of installation of the 1st, 2nd piezoelectric element and the adjustment piezoelectric element. It is the figure which showed another example of installation of the 1st, 2nd piezoelectric element and the adjustment piezoelectric element. It is explanatory drawing which showed the electrical structure of the electric power generating apparatus of the application example. It is explanatory drawing of the piezoelectric element for adjustment of a modification.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Example:
A-1. Structure of power generator:
A-2. Power generator operation (resonance frequency adjustment):
A-3. Power generator operation (efficient generation of high voltage):
A-4. Power generator operating principle (efficient generation of high voltage):
A-5. Switch switching timing (efficient generation of high voltage):
A-6. Example of piezoelectric element installation:
B. Application example:
C. Variations:
D. Other:

A. Example :
The power generator of the present embodiment will be described with reference to FIGS.

A-1. Structure of the power generator:
FIG. 1 is an explanatory diagram showing the structure of the power generation apparatus 100 of the present embodiment. FIG. 1A shows the mechanical structure of the power generation apparatus 100, and FIG. 1B shows the electrical structure.

  The mechanical structure of the power generation apparatus 100 according to the present embodiment is a cantilever structure in which a beam 104 having a weight 106 provided at a distal end is fixed to a support end 102 on a proximal end side. It is desirable to be fixed in the power generation device 100. Further, a piezoelectric member 108 and a piezoelectric member 114 formed of a piezoelectric material such as lead zirconate titanate (PZT) are attached to the surface of the beam 104. The surface of the piezoelectric member 108 includes a front side and a back side. Further, a first electrode 109a and a second electrode 109b formed of a metal thin film are respectively provided. The piezoelectric member 108, the first electrode 109a, and the second electrode 109b constitute a piezoelectric element (hereinafter referred to as a first piezoelectric element). Similarly, the piezoelectric member 114 is provided with a first electrode 115a and a second electrode 115b formed of a metal thin film. The piezoelectric member 114, the first electrode 115a, and the second electrode 115b constitute a piezoelectric element (hereinafter referred to as an adjustment piezoelectric element).

  In the example shown in FIG. 1A, the length (longitudinal direction of the beam 104) and width (longitudinal direction of the support end 102) of the piezoelectric member 114 are the same as those of the piezoelectric member 108. However, the piezoelectric member 114 and the piezoelectric member 108 may be different in at least one of length and width. In the example shown in FIG. 1A, the piezoelectric member 108 is provided on the upper surface side of the beam 104 and the piezoelectric member 114 is provided on the lower surface side. However, the surfaces on which these piezoelectric members are provided are opposite to each other. There may be. Moreover, you may provide in the same surface of a piezoelectric member so that it may mention later. Here, the piezoelectric member 108 and the piezoelectric member 114 are installed on the beam 104 and are deformed by the deformation of the beam 104. The beam 104 corresponds to the “deformable member” of the present invention.

  The beam 104 is fixed to the support end 102 at the base end side, and a weight 106 is provided at the tip end side. Therefore, when vibration or the like is applied, the beam 104 is shown by a white arrow in the figure. The tip of oscillates greatly. As a result, compressive force and tensile force act alternately on the piezoelectric member 108 and the piezoelectric member 114 attached to the surface of the beam 104. Each of the piezoelectric member 108 and the piezoelectric member 114 generates positive and negative charges due to the piezoelectric effect, the charge of the piezoelectric member 108 is applied to the first electrode 109a and the second electrode 109b, and the charge of the piezoelectric member 114 is applied to the first electrode 115a and the second electrode 115b. Appears on electrode 115b. Further, although the weight 106 is not essential, it is desirable that the weight balance is not balanced between the distal end side and the proximal end side of the beam 104. This is because the balance of the weight is not balanced, for example, the displacement of the beam 104 is easily repeated by one vibration.

  FIG. 1B illustrates a circuit diagram of the power generation apparatus 100 of the present embodiment. The piezoelectric member 108 can be electrically expressed as a current source and a capacitor Cg that stores electric charge. Similarly, the piezoelectric member 114 can also be represented as a current source and a capacitor Ca that stores electric charge.

  The first electrode 109a and the second electrode 109b provided on the piezoelectric member 108 are connected to a full-wave rectifier circuit 120 including four diodes D1 to D4. Further, the full-wave rectifier circuit 120 is connected to a capacitor (storage element C1) for storing the rectified current in order to drive an electric load. In this embodiment, the first piezoelectric element is used as a power generating piezoelectric element.

  The first electrode 115 a and the second electrode 115 b that are a pair of electrodes of the adjustment piezoelectric element are connected by a variable resistor 116. The resonance frequency adjusting means 119 of this embodiment includes an adjusting piezoelectric element and a variable resistor 116. The resistance value of the variable resistor 116 is changed by a control signal from the control circuit 112 (corresponding to control means).

  When the beam 104 vibrates, the adjustment piezoelectric element is also deformed, and positive and negative charges appear on the first electrode 115a and the second electrode 115b due to the piezoelectric effect. Here, both electrodes are connected via a variable resistor 116. For example, when the resistance value of the variable resistor 116 is reduced, the charge generated by the deformation of the adjustment piezoelectric element immediately flows into the other electrode via the variable resistor 116. Then, the electric charges generated in both electrodes are reduced, and a force acts in a direction in which the distortion of the adjusting piezoelectric element is restored. That is, the deformable member is not easily distorted, and the resonance frequency is increased. That is, the resonance frequency of the deformable member can be adjusted to increase as the resistance value decreases. When adjustment is not necessary, the resistance value may be set to a sufficiently large value so that the flow of electric charge through the variable resistor 116 is eliminated.

  Here, the control circuit 112 receives displacement information from the displacement detection means 140. The displacement information is information related to displacement caused by deformation of the deformable member (beam 104). In this embodiment, it is assumed that the tip of the beam 104 is repeatedly vibrated and only the amplitude is used as the displacement information. For example, the control circuit 112 generates a control signal that specifies a resistance value such that the amplitude becomes a maximum value. With the power generation device 100 having such a structure, the frequency of environmental vibration and the resonance frequency of the deformable member can be adjusted to be the same.

  In the power generator of this embodiment, the first piezoelectric element forms a resonance circuit together with the inductor L, and the switch SW is provided in the resonance circuit. And the control circuit 112 enables generation | occurrence | production of an efficient high voltage by determining the timing which makes switch SW a conduction | electrical_connection state based on displacement information. The operation of the switch SW of the resonance circuit will be described later. First, matters relating to adjustment of the resonance frequency of the deformable member (beam 104) will be described.

A-2. Power generator operation (resonance frequency adjustment):
FIG. 2 is a diagram illustrating charging of the electricity storage element C1 of this example. As described above, the first piezoelectric element is used as a power generation piezoelectric element. Here, the amount of generated charge increases as the deformation amount of the first piezoelectric element increases. That is, in order to increase the power generation amount, the beam 104 needs to be greatly distorted.

  Here, in the present embodiment, the first electrode 109 a and the second electrode 109 b of the first piezoelectric element are connected to the full-wave rectifier circuit 120. Then, the rectified current is stored in the storage element C1. Here, the potential difference Vgen (see FIG. 1B) between the first electrode 109a and the second electrode 109b is the voltage VC1 between the terminals of the storage element C1 and the forward voltage drop of the diode constituting the full-wave rectifier circuit 120. If the sum of Vf and the sum is larger than VC1 + 2Vf, the electric charge generated thereafter can be taken out as a direct current and stored in the storage element C1.

  For example, in FIG. 2A, since the environmental vibration frequency and the resonance frequency of the beam 104 do not match, the vibration amplitude of the beam 104 is small, and the potential difference Vgen generated by the piezoelectric effect in the first piezoelectric element is VC1 + 2Vf. Is also small. At this time, the storage element C1 is not charged.

  Here, if the frequency of the environmental vibration and the resonance frequency of the beam 104 can be adjusted to coincide with each other, the amplitude of the vibration of the beam 104 can be increased and the potential difference Vgen can be made larger than VC1 + 2Vf as shown in FIG. There is. At this time, the charge in the hatched portion exceeding VC1 + 2Vf can be taken out as a direct current and stored in the storage element C1.

  As described above, the control circuit 112 sets the resistance value of the variable resistor 116 to an appropriate value according to the control signal. That is, the resonance frequency of the beam 104 is adjusted to match the frequency of environmental vibration. Here, the determination of the “appropriate value” of the resistance value is performed based on actual environmental vibration, for example, when the power generator is first placed at the installation location or every time a predetermined time has elapsed since installation. Are preferred.

  FIG. 3A shows the displacement Di of the beam 104. The beam 104 repeats vibration with amplitude u due to environmental vibration. Here, when the frequency of the environmental vibration and the resonance frequency of the beam 104 become the same, the beam 104 vibrates greatly, and the amplitude u takes a maximum value. Therefore, the control circuit 112 sweeps the resistance value R of the variable resistor 116 from the minimum value Rmin to the maximum value Rmax by changing the control signal while receiving the amplitude u as the displacement information from the displacement detection means 140. Then, a change in the amplitude u is measured, and a resistance value that makes the amplitude u a maximum value is obtained.

  FIG. 4 shows an example representing the relationship between the amplitude u and the resistance value R. At this time, when the resistance value of the variable resistor 116 is R0, the frequency of the environmental vibration and the resonance frequency of the beam 104 become the same, and the amplitude u of the beam 104 takes the maximum value u0. The control circuit 112 measures such a change in the amplitude u, and then generates a control signal for setting the resistance value to R0 and outputs the control signal to the variable resistor 116.

  Here, the control circuit 112 stores the amplitude u when the resistance value of the variable resistor 116 is swept from the minimum value Rmin to the maximum value Rmax in a memory or the like, and performs a size comparison after all values are obtained. The maximum value u0 may be determined. Further, the control circuit 112 obtains the differential value of the amplitude u while sweeping the resistance value of the variable resistor 116 from the minimum value Rmin to the maximum value Rmax, and sets the value of the amplitude u when the sign of the differential value changes to the maximum value. It is good.

  The displacement detection means 140 that provides the displacement information to the control circuit 112 is, for example, a displacement sensor, and may directly measure the displacement of the beam 104. Using a displacement sensor makes it possible to measure with high accuracy. At this time, the displacement sensor may be installed in the housing above or below the tip portion of the beam 104. As a type of the displacement sensor, for example, a non-contact type eddy current sensor or an optical sensor having a high response frequency may be used.

  However, when a displacement sensor is used as the displacement detection means 140, the size of the power generation device may increase depending on the type of the displacement sensor. Therefore, a means for detecting a signal having a correlation with the displacement of the beam 104 may be used as the displacement detection means 140, and the signal (especially its amplitude in the case of adjusting the resonance frequency) may be output as the displacement information.

  For example, FIG. 3B and FIG. 3C show the potential difference Vpzt and current Ipzt of the piezoelectric elements installed on the beam 104, which are generated corresponding to the displacement Di of the beam 104 (FIG. 3A), respectively. Represents. The “piezoelectric element installed on the beam 104” includes the first piezoelectric element and the adjustment piezoelectric element, and when the second piezoelectric element is installed on the beam 104 as described later (see FIG. 5). And a second piezoelectric element.

  As shown in FIG. 3B and FIG. 3C, the potential difference Vpzt and the current Ipzt each have a sine curve, and each of the amplitudes v and i takes a maximum value corresponding to the maximum value of the amplitude u. . That is, when the amplitude of vibration of the beam 104 is a maximum value, the piezoelectric element installed on the beam 104 is also greatly deformed, so that the amount of charge appearing at the electrode of the piezoelectric element is also maximized. Then, the potential difference Vpzt, the amplitude v of the current Ipzt, and the amplitude i also take local maximum values. At this time, the control circuit 112 that receives the displacement information can obtain the maximum values for the amplitude v and the amplitude i by a method similar to that for obtaining the maximum value of the amplitude u.

  Therefore, the displacement detection means 140 may be a voltage detection circuit of a piezoelectric element installed on the beam 104. For example, the amplitude v of the potential difference between the first electrode 109a and the second electrode 109b may be output as displacement information. Further, the displacement detection means 140 may be a current detection circuit of a piezoelectric element installed on the beam 104. For example, the amplitude i of the current flowing from the first electrode 109a of the piezoelectric member 108 to the anode of the diode D1 may be output as displacement information. The displacement detection means 140 of the present embodiment is specifically a voltage detection circuit, and the configuration thereof will be described later.

  Note that when the amplitude of vibration of the beam 104 is a maximum value, the amount of charge charged in the power storage element C1 is also a maximum. Therefore, the displacement detection means 140 is a storage voltage detection circuit (not shown), and may output the inter-terminal voltage VC1 of the storage element C1 to the control circuit 112 as displacement information.

  As described above, the power generation apparatus 100 according to the present embodiment can adjust the resonance frequency of the deformable member in accordance with the environmental vibration at the installation location so that the deformable member greatly vibrates. Therefore, a large amount of power generation can be obtained regardless of the installation location. At this time, since the mechanical resonance frequency is adjusted by electrical control using the piezoelectric effect, the size of the device (circuit scale) compared to a case where a mechanism for mechanically adjusting the length of the beam is provided, for example. Can be miniaturized.

A-3. Power generator operation (efficient generation of high voltage):
A mechanism in which the power generation apparatus of the present embodiment efficiently generates a high voltage will be described below with reference to FIGS. The same elements as those in FIGS. 1 to 4 are denoted by the same reference numerals, and description thereof is omitted. In the power generation device of the present embodiment, the obtained voltage is not limited to the voltage generated by the electric polarization of the piezoelectric material. At this time, it is not necessary to provide a separate booster circuit, and the power generator can be downsized. That is, the power generation apparatus of this embodiment can generate a high voltage with a small circuit scale while having the above-described resonance frequency adjustment function.

  FIG. 5 is an explanatory diagram showing an electrical structure of the power generation apparatus 100 of the present embodiment. Although it is the same structure as FIG.1 (b), in FIG. 5, the displacement detection means 140 is shown concretely. The displacement detection means 140 includes the piezoelectric member 110 not shown in FIG. 1A, but a specific example of the installation of the piezoelectric member 110 will be described later (see FIGS. 11 to 12). Now, the operation of the power generation device that efficiently generates a high voltage will be described with reference to FIG.

  In the power generation apparatus 100 of the present embodiment, an inductor L is connected in parallel to the piezoelectric member 108 to form an electrical resonance circuit together with the capacitance component (capacitor Cg) of the piezoelectric member 108. A switch SW for turning on / off the resonance circuit is provided in the resonance circuit (in series with the inductor L). ON / OFF of the switch SW is controlled by the control circuit 112.

  In the power generation apparatus 100 of the present embodiment, the displacement detection unit 140 includes a second piezoelectric element and a voltage detection circuit 124. The second piezoelectric element includes a piezoelectric member 110, a first electrode 111a, and a second electrode 111b. As shown in FIG. 5, the piezoelectric member 110 can be electrically expressed as a current source and a capacitor Cs that stores electric charge. The second piezoelectric element is also installed on the beam 104 in the same manner as the first piezoelectric element and the adjustment piezoelectric element.

  The voltage detection circuit 124 detects the voltage between the electrodes of the second piezoelectric element having a correlation with the displacement of the beam 104 and outputs the detected voltage to the control circuit 112 as displacement information. Here, the displacement information includes not only the amplitude v (see FIG. 3B) but also a signal representing the peak (extreme value) of the output voltage of the second piezoelectric element.

  The control circuit 112 determines the resistance value of the variable resistor 116 based on the change in the amplitude v as described above so that the resonance frequency of the beam 104 matches the frequency of the environmental vibration. Further, the control circuit 112 of this embodiment controls ON / OFF of the switch SW based on a signal representing the peak of the output voltage of the second piezoelectric element.

  In the power generation apparatus 100 of the present embodiment, by appropriately controlling ON / OFF of the switch SW, a high voltage can be generated with a small circuit scale without providing a separate booster circuit. In the following, a description will be given of appropriate control and the like for ON / OFF of the switch SW for this purpose.

  FIG. 6 is an explanatory diagram showing the operation of the power generation apparatus 100 of the present embodiment. 6A shows how the displacement of the tip of the beam 104 changes as the beam 104 vibrates. A positive displacement (u) represents a state in which the beam 104 is warped upward (a state in which the upper surface side of the beam 104 is concave), and a negative displacement (−u) is a state in which the beam 104 is warped downward. (A state where the lower surface side of the beam 104 is concave). FIG. 6B shows the state of current generated by the piezoelectric member 108 as a result of the deformation of the beam 104 and the electromotive force generated inside the piezoelectric member 108 as a result. In FIG. 6B, the state in which electric charges are generated in the piezoelectric member 108 is represented as the amount of electric charges generated per unit time (that is, the current Ipzt), and the electromotive force generated in the piezoelectric member 108 is the first electrode. This is expressed as a potential difference Vpzt generated between 109a and the second electrode 109b.

  As described above, the piezoelectric member 110 is also provided on the beam 104, and when the beam 104 is deformed, the piezoelectric member 110 is also deformed similarly to the piezoelectric member 108. Therefore, the current Ipzt and the potential difference Vpzt shown in FIG. 6B are also generated inside the piezoelectric member 110, just like the piezoelectric member 108.

  As shown in FIGS. 6A and 6B, while the displacement of the beam 104 is increasing, the piezoelectric member 108 generates a current in the positive direction (that is, the current Ipzt is a positive value), Along with this, the potential difference Vpzt between the first electrode 109a and the second electrode 109b increases in the positive direction. If the potential difference Vpzt in the positive direction becomes larger than the sum of the inter-terminal voltage VC1 of the storage element C1 and twice the forward drop voltage Vf of the diode constituting the full-wave rectifier circuit 120, that is, VC1 + 2Vf, The charges generated thereafter can be taken out as a direct current and stored in the storage element C1. In addition, while the displacement of the beam 104 is decreasing, the piezoelectric member 108 generates a negative current (that is, the current Ipzt is a negative value), and accordingly, the potential difference between the first electrode 109a and the second electrode 109b. Vpzt increases in the negative direction. If the potential difference Vpzt in the negative direction is larger than the sum of VC1 and 2Vf of the full-wave rectifier circuit 120, the generated charge can be taken out as a direct current and stored in the storage element C1. That is, even when the switch SW in FIG. 5 is kept OFF, electric charge can be stored in the power storage element C1 for the portion indicated by hatching in FIG. 6B.

  In the power generation apparatus 100 of the present embodiment, the switch SW is turned on at the timing shown in FIG. Then, as shown in FIG. 6D, the voltage waveform between the terminals of the piezoelectric element including the piezoelectric member 108 (hereinafter simply referred to as between the terminals of the piezoelectric member 108) is shifted when the switch SW is turned on. Such a phenomenon occurs. For example, in the period B indicated as “B” in FIG. 6D, the voltage waveform Vpzt indicated by the thin broken line corresponding to the electromotive force of the piezoelectric member 108 is indicated by a thick broken line that is shifted in the negative direction. A voltage waveform appears between the terminals of the piezoelectric member 108. The reason why such a phenomenon occurs will be described later. Further, in the period C indicated as “C” in FIG. 6D, a thick broken voltage waveform appears such that the voltage waveform Vpzt corresponding to the electromotive force of the piezoelectric member 108 is shifted in the positive direction. Similarly, in the subsequent period D, period E, period F, and the like, the voltage waveform Vpzt corresponding to the electromotive force of the piezoelectric member 108 is shifted in the positive direction or the negative direction, and a thick broken voltage waveform appears. Then, in the portion where the shifted voltage waveform exceeds the sum of VC1 and 2Vf (the portion shown by hatching in FIG. 6D), the charge generated in the piezoelectric member 108 is stored in the storage element C1. I can keep it. As a result of the electric charge flowing from the piezoelectric member 108 to the power storage element C1, the voltage between the terminals of the piezoelectric member 108 is clipped by the sum of VC1 and 2Vf. In other words, the voltage between the terminals of the piezoelectric member 108 is held at the sum of VC1 and 2Vf. As a result, the voltage waveform between the first electrode 109a and the second electrode 109b is a waveform indicated by a thick solid line in FIG.

  Comparison between the case where the switch SW shown in FIG. 6B is kept OFF and the case where the switch SW is turned ON at the timing when the deformation direction of the beam 104 is switched as shown in FIG. 6D. As will be apparent, in the power generation apparatus 100 of the present embodiment, it is possible to efficiently store charges in the power storage element C1 by turning on the switch SW at an appropriate timing. Therefore, in order to turn on the switch SW at an appropriate timing, the power generation apparatus 100 of this embodiment is provided with a control piezoelectric member 110, detects the voltage of the piezoelectric member 110, and controls the switch SW. Yes. This point will be described in detail later.

  In addition, when charge is stored in the storage element C1 and the voltage across the storage element C1 increases, the amount of shift in the voltage waveform increases accordingly. For example, a period B in FIG. 6D (a state where no charge is stored in the power storage element C1) and a period H in FIG. 6D (a state where a small amount of charge is stored in the power storage element C1) are included. In comparison, the shift amount of the voltage waveform is larger in the period H. Similarly, when the period C and the period I in FIG. 6D are compared, the shift amount of the voltage waveform is larger in the period I in which the charge stored in the power storage element C1 is increasing. The reason why such a phenomenon occurs will be described later. As a result, in the power generation apparatus 100 according to the present embodiment, the piezoelectric member 108 is deformed to be generated between the first electrode 109a and the second electrode 109b. A voltage equal to or higher than the voltage Vpzt can also be stored in the power storage element C1. As a result, it is not necessary to provide a special booster circuit, and a small and highly efficient power generator can be obtained.

A-4. Power generator operating principle (efficient generation of high voltage):
FIG. 7 is an explanatory diagram conceptually showing the first half of the operating principle of the power generation apparatus 100 of the present embodiment. Moreover, FIG. 8 is explanatory drawing which showed notionally the latter half part of the operation principle of the electric power generating apparatus 100 of a present Example. 7 and 8 conceptually show the movement of charges in Cg (the capacitor of the piezoelectric member 108) when the switch SW is turned on in accordance with the deformation of the piezoelectric member 108. FIG. FIG. 7A shows a state in which the piezoelectric member 108 (exactly, the beam 104) is deformed upward (so that the upper surface side is concave). When the piezoelectric member 108 is deformed upward, a positive current flows from the current source, charges are accumulated in Cg (the capacitor of the piezoelectric member 108), and Vgen generates a positive voltage. The voltage value increases as the deformation amount of the piezoelectric member 108 increases. Then, the switch SW is turned on at the timing when the deformation amount of the piezoelectric member 108 becomes the extreme value (the timing when the charge amount becomes the extreme value (see FIG. 7B)).

  FIG. 7C shows a state immediately after the switch SW is turned on. Since electric charge is stored in Cg (the capacitor of the piezoelectric member 108), this electric charge tends to flow to the inductor L. When a current flows through the inductor L, a magnetic flux is generated (the magnetic flux increases), but the inductor L has a property (self-inducing action) in which a counter electromotive force is generated in a direction that prevents a change in the magnetic flux passing through the inductor L. When the switch SW is turned on, the magnetic flux tends to increase due to the flow of electric charge, so that a back electromotive force is generated in a direction that prevents the increase of the magnetic flux (in other words, a direction that prevents the flow of electric charge). The magnitude of the back electromotive force is proportional to the magnetic flux change rate (change amount per unit time). In FIG. 7C, the back electromotive force generated in the inductor L in this way is represented by a hatched arrow. Since such a back electromotive force is generated, even if the switch SW is turned on, the electric charge of the piezoelectric member 108 flows out little by little. That is, the current flowing through the inductor L increases little by little.

  Thereafter, when the current flowing through the inductor L reaches a peak, the rate of change of the magnetic flux becomes “0”, so that the counter electromotive force becomes “0” as shown in FIG. This time, the current starts to decrease. Then, since the magnetic flux penetrating through the inductor L is reduced, an electromotive force is generated in the inductor L in a direction that prevents the magnetic flux from decreasing (direction in which a current is to flow) (see FIG. 7E). As a result, the current continues to flow through the inductor L while drawing electric charges from Cg (the capacitor of the piezoelectric member 108) by this electromotive force. If no loss occurs during the movement of the charge, all the charges generated by the deformation of the piezoelectric member 108 move and the positive and negative charges are replaced (that is, the lower surface side of the piezoelectric member 108). In this state, positive charges are distributed and negative charges are distributed on the upper surface side. FIG. 7F shows a state where all the positive and negative charges generated by the deformation of the piezoelectric member 108 have moved.

  If the switch SW is turned on as it is, a phenomenon opposite to the above-described content occurs. That is, the positive charge on the lower surface side of the piezoelectric member 108 tends to flow to the inductor L, and at this time, a counter electromotive force is generated in the inductor L in a direction that prevents the flow of charges. Thereafter, when the current flowing through the inductor L reaches a peak and then starts to decrease, an electromotive force is generated in the inductor L in a direction that prevents the current from decreasing (a direction in which the current continues to flow). As a result, all positive charges on the lower surface side of the piezoelectric member 108 are moved to the upper surface side (the state shown in FIG. 7B). The positive charge thus returned to the upper surface side of the piezoelectric member 108 again moves to the lower surface side as described above with reference to FIGS. 7B to 7F.

  As described above, when the switch SW is turned on in a state where electric charges are stored in Cg (the capacitor of the piezoelectric member 108) and the state is maintained, the direction of the current flows between the piezoelectric member 108 and the inductor L. A kind of resonance phenomenon that reverses alternately occurs. Since the period of this resonance phenomenon is the resonance period T of the so-called LC resonance circuit, the size (capacitance) of Cg (capacitor of the piezoelectric member 108) is represented by C, and the size (inductance) of the inductive component of the inductor L is represented by C. Let L be given by T = 2π (LC) 0.5. Accordingly, the time from immediately after the switch SW is turned on (the state shown in FIG. 7C) to the state shown in FIG. 7F is T / 2.

  Therefore, when T / 2 has elapsed since the switch SW was turned on, the switch SW is turned off as shown in FIG. From this state, the piezoelectric member 108 (more precisely, the beam 104) is deformed downward (so that the lower surface side is concave). In FIG. 7A, the piezoelectric member 108 is deformed upward, but in FIG. 8A, the piezoelectric member 108 is deformed downward. Therefore, a negative current flows from the current source, and Vgen increases in the negative direction. Thus, charges accumulate in Cg. Further, as described above with reference to FIGS. 7A to 7F, the piezoelectric member 108 (precisely, the beam 104) is not positively connected to the lower surface side of the piezoelectric member 108 before the piezoelectric member 108 is deformed downward. Since charges are distributed and negative charges are distributed on the upper surface side, in addition to these charges, new positive charges are accumulated on the lower surface side, and new negative charges are accumulated on the upper surface side. become. FIG. 8B shows a state in which new charges are accumulated in the piezoelectric member 108 by deforming the piezoelectric member 108 (more precisely, the beam 104) with the switch SW turned off.

  When the switch SW is turned on at the timing when the deformation amount of the piezoelectric member 108 becomes an extreme value (the timing when the charge amount becomes an extreme value), the positive charge accumulated on the lower surface side of the piezoelectric member 108 is applied to the inductor L. Try to flow. At this time, since a counter electromotive force is generated in the inductor L (see FIG. 8C), the current starts to flow little by little, but eventually reaches a peak and then decreases. Then, an electromotive force is generated in the inductor L in a direction that prevents the current from decreasing (a direction in which the current continues to flow) (see FIG. 8E), and the current continues to flow due to this electromotive force. In this state, all positive charges distributed on the lower surface side of the piezoelectric member 108 move to the upper surface side, and all negative charges distributed on the upper surface side move to the lower surface side (FIG. 8 (f )reference). Further, the time required for all the positive charges on the lower surface side to move to the upper surface side and all the negative charges on the upper surface side to move to the lower surface side is a time T / 2 corresponding to a half cycle of the LC resonance circuit. Therefore, after the switch SW is turned on, the switch SW is turned off when the time T / 2 has elapsed, and this time, the piezoelectric member 108 (more precisely, the beam 104) is deformed upward (so that the upper surface side is concave). Then, positive and negative charges can be further accumulated in the piezoelectric member 108.

  As described above, in the power generation apparatus 100 of the present embodiment, after the piezoelectric member 108 is deformed to generate electric charge, the piezoelectric member 108 is connected to the inductor L, and the resonance circuit is provided for a period that is half the resonance period. By forming, the distribution of positive and negative charges in the piezoelectric member 108 is reversed. Thereafter, the piezoelectric member 108 is deformed in the opposite direction to generate a new charge. Since the distribution of positive and negative charges in the piezoelectric member 108 is reversed, the newly generated charge is accumulated in the piezoelectric member 108. Thereafter, again, the piezoelectric member 108 is connected to the inductor L by a half period of the resonance period to reverse the distribution of positive and negative charges in the piezoelectric member 108, and then the piezoelectric member 108 is deformed in the reverse direction. By repeating such an operation, the electric charge accumulated in the piezoelectric member 108 can be increased every time the piezoelectric member 108 is repeatedly deformed.

  Note that if the switch SW is turned off at least when the Vgen has a polarity opposite to that when the switch SW is turned on due to resonance of the LC resonance circuit, the voltage Vgen is boosted. In the above description (and the following description), “T / 2 (half the resonance period)” is used for convenience. However, the present invention is not limited to this, and the switch SW is turned on for the resonance period T of the LC resonance circuit. If the predetermined period is set to at least a time longer than (n + 1/4) T and shorter than (n + 3/4) T (n is an arbitrary integer greater than or equal to 0), Vgen can be boosted efficiently.

  As described above with reference to FIG. 6, in the power generation apparatus 100 of the present embodiment, a phenomenon occurs in which the voltage waveform between the terminals of the piezoelectric member 108 is shifted each time the switch SW is turned on. That is, for example, in the period A shown in FIG. 6D, a voltage is generated between the first electrode 109a and the second electrode 109b in accordance with the deformation of the piezoelectric member 108 (more precisely, the beam 104). Since the electrode 109a and the second electrode 109b are connected to the full-wave rectifier circuit 120, the charge exceeding the sum of VC1 and 2Vf flows into the storage element C1 connected to the full-wave rectifier circuit 120. . As a result, when the switch SW is turned ON when the deformation amount of the beam 104 reaches an extreme value, the positive and negative charges remaining in the piezoelectric member 108 at that time move through the inductor L, and the piezoelectric member 108 The arrangement of the positive and negative charges at is reversed. As is clear from the mechanism described above with reference to FIGS. 7 and 8, the period during which the switch SW is turned on is half the resonance period of the resonance circuit constituted by the capacitor of the piezoelectric member 108 and the inductor L. It will be time.

  When the beam 104 is deformed in the reverse direction from the state where the arrangement of positive and negative charges is changed, a voltage waveform due to the piezoelectric effect appears between the first electrode 109a and the second electrode 109b of the piezoelectric member 108. That is, a voltage change due to deformation occurs in the piezoelectric member 108 from the state where the polarities of the first electrode 109a and the second electrode 109b of the piezoelectric member 108 are interchanged. As a result, in the period B shown in FIG. 6D, a voltage waveform appears in which the voltage waveform generated in the piezoelectric member 108 due to the deformation of the beam 104 is shifted. However, as described above, since the charge in the portion exceeding the sum of the voltages VC1 and 2Vf flows into the storage element C1, the voltage between the first electrode 109a and the second electrode 109b of the piezoelectric member 108 is VC1 and Clipped with the sum of 2Vf. Thereafter, when the switch SW is turned on for half the resonance period, the arrangement of positive and negative charges remaining in the piezoelectric member 108 is replaced. When the beam 104 is deformed from this state, a voltage waveform due to the piezoelectric effect appears on the piezoelectric member 108. For this reason, even during the period C shown in FIG. 6D, a voltage waveform appears as if the voltage waveform due to the deformation of the beam 104 is shifted.

  Further, as described above with reference to FIG. 6, in the power generation apparatus 100 of the present embodiment, a phenomenon in which the shift amount of the voltage waveform gradually increases while the beam 104 is repeatedly deformed occurs. For this reason, the great effect that the voltage higher than the electric potential difference produced between the 1st electrode 109a and the 2nd electrode 109b by the piezoelectric effect of the piezoelectric member 108 can be stored in the electrical storage element C1 can be acquired. Such a phenomenon is caused by the following mechanism.

  First, as shown in the period A or the period B in FIG. 6D, when the power storage element C1 is not charged, the voltage generated between the terminals of the piezoelectric member 108 is 2Vf of the full-wave rectifier circuit 120. Since the charge flows from the piezoelectric member 108 to the storage element C1, the voltage appearing between the terminals of the piezoelectric member 108 is clipped at 2Vf. However, as the electric charge is stored in the electric storage element C1, the voltage between the terminals of the electric storage element C1 increases. Then, after that, the electric charge starts to flow from the piezoelectric member 108 until the voltage between the terminals of the power storage element C1 becomes higher than the sum of VC1 and 2Vf. For this reason, the value at which the voltage between the terminals of the piezoelectric member 108 is clipped gradually increases as charges are stored in the power storage element C1.

  In addition, as described above with reference to FIGS. 7 and 8, unless the electric charge flows out from the piezoelectric member 108, the electric charge in the piezoelectric member 108 increases every time the piezoelectric member 108 (more precisely, the beam 104) is deformed. However, the voltage between the terminals of the piezoelectric member 108 increases. Therefore, according to the power generation apparatus 100 of the present embodiment, it is possible to generate power in a state where the voltage is naturally boosted to a voltage necessary for driving the electric load without providing a special booster circuit.

A-5. Switch switching timing (efficient generation of high voltage):
As described above, in the power generation apparatus 100 of this embodiment, when the piezoelectric member 108 (exactly, the beam 104) is repeatedly deformed and the deformation direction is switched, the piezoelectric member is only half the resonance period. By connecting 108 to the inductor L, it is possible to obtain an excellent feature that the efficiency is good and, in addition, the step-up circuit is unnecessary, and thus the size can be easily reduced. However, it is not so easy to turn on the switch SW when the deformation direction of the beam 104 is switched. For example, when the deformation direction of the beam 104 is switched, if the magnitude of the displacement of the beam 104 is considered to be the maximum, a mechanical contact is used to turn ON when the beam 104 reaches the maximum displacement. It is also possible to do. However, if the contact adjustment is shifted, the efficiency is greatly reduced. Therefore, in the power generation apparatus 100 of this embodiment, not only the piezoelectric member 108 for power generation but also the piezoelectric member 110 for control is provided, and the switch SW is controlled by detecting the voltage generated in the piezoelectric member 110. ing.

  Here, referring to FIG. 3 again, the reason why the switch SW can be controlled at an appropriate timing by detecting the voltage generated in the control piezoelectric member 110 will be described. FIG. 3A shows the displacement of the beam 104. FIG. 3B shows how the electromotive force Vpzt generated in the piezoelectric member 110 changes with the vibration of the beam 104.

  As described above with reference to FIGS. 7 and 8, when the switch SW is turned on at the timing when the displacement of the beam 104 reaches the extreme value, the most efficient power generation can be achieved. As apparent from a comparison between FIG. 3A and FIG. 3B, the displacement of the beam 104 has an extreme value that coincides with the timing at which the electromotive force Vpzt of the piezoelectric member 110 has an extreme value. To do. This is due to the following reason. First, even if electric charges are generated in the piezoelectric member 108 due to deformation, the electromotive force Vpzt of the piezoelectric member 108 is determined by the displacement of the beam 104 due to the influence of the electric charge being drawn out by the inductor L or the electric charge flowing into the power storage element C1. It will not be exactly the same. On the other hand, since the piezoelectric member 110 is not connected to the inductor L or the power storage element C1, the increase or decrease in electric charge is directly reflected in the change in the electromotive force Vpzt of the piezoelectric member 110. For this reason, the timing when the electromotive force Vpzt of the piezoelectric member 110 becomes an extreme value coincides with the timing when the displacement of the beam 104 becomes the extreme value.

  Therefore, as indicated by an arrow in FIG. 3B, the timing at which the electromotive force Vpzt of the piezoelectric member 110 becomes an extreme value is detected. Then, as shown in FIG. 3 (d), if the switch SW is turned on for the half time (T / 2) of the above-described resonance period from that timing, it is possible to generate power efficiently.

  FIG. 9 is a flowchart showing the control processing of this embodiment. In this embodiment, the control circuit 112 performs these processes. Note that the control circuit 112 may be a CPU.

  When the power generation apparatus is installed or when a predetermined time has elapsed since installation, the resonance frequency of the deformable member is adjusted in accordance with the environmental vibration. Steps S2, S4, S6, and S8 in FIG. 9 represent the control process at this time. First, the resonance frequency changes due to the change in the resistance value of the variable resistor 116 included in the resonance frequency adjusting means 119 (step S2). Here, the change in the resonance frequency is a change that occurs when the resistance value of the variable resistor 116 gradually increases with time from, for example, the minimum value Rmin (see FIG. 4). That is, the resonance frequency is gradually lowered. At this time, the control circuit 112 may adjust the control signal output to the variable resistor 116 to gradually increase the resistance value of the variable resistor 116.

  At this time, the control circuit 112 receives displacement information from the displacement detection means 140 (step S4). The displacement information here is the voltage between the electrodes of the second piezoelectric element (see FIG. 5). As described above, when the vibration amplitude of the beam 104 takes a maximum value, the amplitude of the voltage between the electrodes of the second piezoelectric element also takes a maximum value. The control circuit 112 determines the maximum value of the amplitude of the displacement information (voltage) while changing the resistance value of the variable resistor 116 (step S6). Until the maximum value is obtained, the control circuit 112 changes the resonance frequency (step S6: no). For example, the control circuit 112 may obtain a differential value of the amplitude and determine that the amplitude when the sign of the differential value changes is a maximum value.

  Then, after the maximum value is obtained (step S6: yes), the control circuit 112 generates a control signal that specifies a resistance value that makes the amplitude maximum, and outputs the control signal to the variable resistor 116 (S8). With these control processes, the frequency of the environmental vibration at the installation location and the resonance frequency of the deformable member are combined so that the deformable member vibrates greatly. As a result, a large amount of power generation can be obtained. Then, a switch control process (step S10) is performed next, and a high voltage can be generated with a small circuit scale without providing a separate booster circuit.

  FIG. 10 is a flowchart showing details of the switch control process (step S10). In the switch control process, the electromotive force of the control piezoelectric member 110 is detected, and the switch SW is turned ON / OFF.

  When the switch control process is started, the control circuit 112 determines whether or not the voltage value has reached a peak based on the signal from the voltage detection circuit 124 that detects the output voltage of the second piezoelectric element (that is, the voltage value is It is determined whether or not an extreme value has been reached (step S100). The voltage detection circuit 124 may differentiate the voltage waveform, for example, and determine whether or not the voltage value has reached a peak from the change in the sign of the differential value.

  When the peak of the output voltage of the second piezoelectric element is detected (step S100: yes), the switch SW of the resonance circuit (resonance circuit constituted by the capacitor Cg and the inductor L of the piezoelectric member 108) is turned ON (step S100). (S102), a timer (not shown) built in the control circuit 112 is started (step S104). Then, it is determined whether or not a half of the resonance period of the resonance circuit constituted by the capacitor Cg and the inductor L of the piezoelectric member 108 has elapsed (step S106). If the peak of the output voltage of the second piezoelectric element is not detected (step S100: no), the process waits until it is detected.

  As a result, when it is determined that the time of 1/2 of the resonance period has not elapsed (step S106: no), the same determination is repeated as it is, thereby waiting until the time of 1/2 of the resonance period has elapsed. It becomes a state. Then, when it is determined that the time of 1/2 of the resonance period has elapsed (step S106: yes), the switch SW of the resonance circuit is turned off (step S108). Thereafter, returning to the head of the switch control process, the above-described series of processes is repeated.

  If the switch SW of the resonance circuit is turned on / off as described above, the switch SW can be easily turned on / off at an appropriate timing in accordance with the movement of the beam 104. It is possible to generate electricity well.

A-6. Example of piezoelectric element installation:
In the power generation apparatus 100 of the present embodiment described above, the first piezoelectric element, the adjustment piezoelectric element, and the second piezoelectric element are installed on the same deformable member (beam 104). Depending on how they are installed, there is a difference in power generation capacity. Below, with reference to FIGS. 11-12, the example of some installation is demonstrated. In addition, the same code | symbol is attached | subjected about the same element as FIGS. 1-10, and description is abbreviate | omitted.

  FIG. 11 is an explanatory diagram showing an installation example in the case where the first piezoelectric element and the adjustment piezoelectric element are provided on different surfaces of the beam 104. FIG. 11A is a plan view seen from one surface of the beam 104. FIG. 11B is a plan view seen from the other surface of the beam 104. FIG. 11A shows the piezoelectric member 108 and the first electrode 109a, and the piezoelectric member 110 and the first electrode 111a provided on one surface of the beam 104. FIG. The piezoelectric member 108 and the first electrode 109a are constituent elements of the first piezoelectric element, and the piezoelectric member 110 and the first electrode 111a are constituent elements of the second piezoelectric element. FIG. 11B shows the piezoelectric member 114 and the second electrode 115 b provided on the other surface of the beam 104. The piezoelectric member 114 and the second electrode 115b are components of the adjustment piezoelectric element.

  At this time, the area of the adjustment piezoelectric element can be increased. Therefore, it is possible to increase the adjustment capability of the resonance frequency of the beam 104.

  Next, FIG.11 (c) and FIG.11 (d) are another installation examples. FIG. 11C is a plan view seen from one surface of the beam 104. FIG. 11D is a plan view seen from the other surface of the beam 104. FIG. 11C shows the piezoelectric member 108 and the first electrode 109 a provided on one surface of the beam 104. FIG. 11D shows the piezoelectric member 114 and the second electrode 115b, and the piezoelectric member 110 and the second electrode 111b provided on the other surface of the beam 104. In this case as well, the first piezoelectric element and the adjustment piezoelectric element are provided on different surfaces of the beam 104. Unlike the example shown in FIGS. The area of the first piezoelectric element used as can be increased. As a result, the power generation capacity can be increased.

  FIG. 12 is an explanatory view showing an installation example in the case where the first piezoelectric element and the adjustment piezoelectric element are provided on the same surface of the beam 104. When the first piezoelectric element and the adjustment piezoelectric element are provided on the same surface of the deformable member, the second piezoelectric element can be independently installed on the other surface of the beam 104.

  FIG. 12A is an installation example in the case where the first piezoelectric element and the adjustment piezoelectric element are provided on the same surface of the beam 104, and is a plan view seen from one surface of the beam 104. FIG. 12A shows the piezoelectric member 108 and the first electrode 109a, and the piezoelectric member 114 and the first electrode 115a. The piezoelectric member 108 and the first electrode 109a are constituent elements of the first piezoelectric element, and the piezoelectric member 114 and the first electrode 115a are constituent elements of the adjusting piezoelectric element. FIG. 12B is a plan view seen from the other surface of the beam 104. FIG. 12B shows the piezoelectric member 110 and the second electrode 111 b provided on one surface of the beam 104. The piezoelectric member 110 and the second electrode 111b are constituent elements of the second piezoelectric element.

  At this time, the area of the second piezoelectric element can be increased. Therefore, the sensitivity of the second piezoelectric element used as the control piezoelectric element can be increased.

  Such an arrangement of the piezoelectric element makes it possible to increase the adjustment capability of the resonance frequency of the beam 104, increase the power generation capability, or increase the sensitivity of the control piezoelectric element.

B. Application example:
In the above embodiment, the first piezoelectric element forms a resonance circuit together with the inductor, and the resonance circuit is provided with a switch. And the control means has made it possible to generate electric power at a high voltage by determining the timing when the switch is turned on based on the displacement information. However, even if the resonance circuit is not included, by providing the resonance frequency adjusting means, the resonance frequency can be adjusted to increase the power generation efficiency.

  FIG. 13 is an explanatory diagram showing an electrical structure of the power generation apparatus 100A of the application example. In addition, the same code | symbol is attached | subjected to the same element as FIG.1 (b), and description is abbreviate | omitted. As is apparent from a comparison between FIG. 13 and FIG. 1B, the inductor L is not connected to the power generation apparatus 100A of the application example with respect to the above-described embodiment. That is, the LC resonance circuit as in the above-described embodiment is not configured in the power generation apparatus 100A of the application example. Thereby, the control process (switch control process of FIG. 10) for using the LC resonance circuit executed by the CPU built in the control circuit 112 can be omitted.

  Of course, since the power generation apparatus 100A of the application example does not use the LC resonance circuit like the power generation apparatus 100 of the above-described embodiment, the boosting effect unlike the power generation apparatus 100 of the embodiment cannot be expected. However, by including the resonance frequency adjusting means for adjusting the resonance frequency, the resonance frequency of the deformable member can be adjusted in accordance with the environmental vibration. Specifically, as in the embodiment, the control circuit 112 may adjust the resonance frequency of the beam 104 by setting the resistance value of the variable resistor 116 to an appropriate value according to the control signal so as to match the frequency of the environmental vibration. it can.

  For this reason, the power generators of these inventions can adjust the resonance frequency of the deformable member to vibrate the deformable member greatly in accordance with the environmental vibration, and obtain a relatively large amount of power generation, although not as much as the embodiment. it can. At this time, since a mechanism for adjusting the length of the beam mechanically and a plurality of cantilever beams having different lengths are not required, the size of the apparatus can be reduced.

C. Modified example:
The displacement detection means 140 of the above embodiment includes the second piezoelectric element and the voltage detection circuit 124. In this modification, the displacement detection unit 140a of FIG. 14 is used instead of the displacement detection unit 140 of the embodiment. The displacement detection means 140a includes a second piezoelectric element and a current detection circuit 128. As shown in FIG. 3C, the current Ipzt also corresponds to the change of the displacement Di and can be used as displacement information. That is, as shown by the arrow in FIG. 3C, the vibration peak of the beam 104 and the timing at which the direction of the current due to the charge generated by the second piezoelectric element is switched (the timing at which the current becomes 0) correspond to each other. doing. For example, the control circuit 112 may receive a signal indicating the timing when the current becomes 0 from the current detection circuit 128 and turn on the switch SW (see FIG. 5).

  The current detection circuit 128 may be configured by, for example, connecting a current detector, an amplifier circuit, an absolute value circuit, and a comparator in order. The current detector is generally known. For example, a Hall element type current sensor or a shunt resistor can be used. The amplifier circuit amplifies the output signal of the current detector with a predetermined gain. The absolute value circuit outputs an absolute value signal of the output signal of the amplifier circuit. The comparator binarizes (pulses) the output signal of the absolute value circuit and outputs it. The timing when the current becomes 0 can be grasped by the falling edge of the output signal of the comparator.

D. Other:
Although various examples have been described above, the present invention is not limited to these examples, and can be implemented in various modes without departing from the scope of the invention.

  For example, in the above-described embodiments, the piezoelectric member 108 is described as being attached to the cantilever beam 104. However, the member to which the piezoelectric member 108, the piezoelectric member 110, and the like are attached may be any member as long as the member can be easily and repeatedly deformed by vibration or the like. For example, the piezoelectric member 108 or the piezoelectric member 110 may be attached to the surface of the thin film.

  Since the power generation device of the present invention generates power in response to vibration or movement, for example, if a power generation device is installed in a bridge, a building, or a landslide assumption location, it generates power in the event of a disaster such as an earthquake and is necessary for network means such as electronic equipment Power can be supplied only during times (at the time of disaster). At this time, the resonance frequency of the deformable member is adjusted according to the installation location, and efficient power generation can be performed.

  Note that although the power generation device of the present invention can be downsized, the installation target is not limited to an electronic device. For example, by using the power generation device of the present invention for a moving means such as a vehicle or a train, it is possible to generate electric power by vibration accompanying movement and efficiently supply power to the equipment provided in the moving means.

  Furthermore, instead of being installed in a specific device or the like, the power generation device of the present invention may have the same shape as, for example, a button battery or a dry battery, and may be used in general electronic devices. At this time, since the storage element can be charged by vibration, it can be used as a battery even in the event of a loss of power. At this time, since the lifetime is longer than that of the primary battery, it is possible to reduce the environmental load from the viewpoint of the life cycle.

DESCRIPTION OF SYMBOLS 100 ... Power generation device, 102 ... Support end, 104 ... Beam, 106 ... Weight, 108, 110, 114 ... Piezoelectric member, 109a, 111a, 115a ... First electrode, 109b, 111b, 115b ... Second electrode, 112 ... Control Circuit 116, variable resistance, 119, 119a, resonance frequency adjustment means, 120, full-wave rectification circuit, 124, voltage detection circuit, 128, current detection circuit, 140, 140a, displacement detection means, L, inductor, C1, storage Element, D1 to D4 ... Diode, SW ... Switch

Claims (9)

A deformable member that deforms by switching the deformation direction;
A first piezoelectric element provided on the deformable member;
Displacement detecting means for generating displacement information which is information relating to displacement due to deformation of the deformable member;
A resonance frequency adjusting means for adjusting a resonance frequency of the deformation member based on a control signal, including an adjustment piezoelectric element provided on the deformation member;
An inductor constituting a resonance circuit including the first piezoelectric element;
A switch provided in the resonant circuit;
And a control unit configured to generate the control signal based on the displacement information and to turn on the switch for a predetermined period based on the displacement information. The power generator according to claim 1,
The resonance frequency adjusting means includes
Including a variable resistor connected to a pair of electrodes of the adjustment piezoelectric element;
A power generator that changes a resistance value of the variable resistor based on the control signal. In the electric power generating apparatus in any one of Claims 1 thru | or 2,
The displacement detection means includes
A second piezoelectric element provided on the deformable member;
A voltage detection circuit for detecting a voltage generated in the second piezoelectric element,
A power generation device that generates the displacement information based on a voltage detected by the voltage detection circuit. In the electric power generating apparatus in any one of Claims 1 thru | or 2,
The displacement detection means includes
A second piezoelectric element provided on the deformable member;
A current detection circuit for detecting a current flowing from the second piezoelectric element,
A power generation device that generates the displacement information based on a current detected by the current detection circuit. In the electric power generating apparatus in any one of Claims 1 thru | or 4,
The power generation apparatus in which the first piezoelectric element and the adjustment piezoelectric element are provided on different surfaces of the deformable member. In the electric power generating apparatus in any one of Claims 1 thru | or 4,
The power generation apparatus in which the first piezoelectric element and the adjustment piezoelectric element are provided on the same surface of the deformable member. A deformation member that deforms by switching a deformation direction; a first piezoelectric element provided on the deformation member; a displacement detection unit that generates displacement information that is information relating to displacement caused by deformation of the deformation member; and the deformation member A control method of a power generation device comprising: an adjustment piezoelectric element provided; and a resonance frequency adjusting means for adjusting a resonance frequency of the deformable member based on a control signal,
Obtaining the displacement information;
Generating the control signal based on the displacement information.   An electronic device comprising the power generation device according to claim 1.   A moving means including the power generator according to claim 1.

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