JP5871120B2 - Power generation device, power generation device control method, electronic device, and moving means - Google Patents

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). In addition, a technique has been proposed in which a direct current can be obtained without causing a voltage loss in a diode by closing a contact only while a positive charge is generated in a piezoelectric element (patent) Reference 2). If these technologies are used, the power generation device can be reduced in size, and therefore, for example, applications such as incorporation in a small electronic component instead of a battery are expected.

JP-A-7-107752 JP 2005-31269 A

  However, the proposed conventional technique has a problem that the obtained voltage is limited to the voltage generated by the electric polarization of the piezoelectric material. For this reason, in most cases, a separate booster circuit is required, and there is a problem that it is difficult to sufficiently reduce the size of the power generator.

  Further, even when a high voltage is generated by the power generation device, a circuit for boosting generally requires control by a switch. However, in order to switch the switch to the ON or OFF state, it is necessary to prepare, for example, a storage element in the power generation device and store a certain amount of charge. Therefore, it is preferable that the power generation device also has a function of reliably storing charges for turning on or off the switch in the discharged storage element at the start of operation. Otherwise, an auxiliary power source (battery or the like) is required to turn the switch on or off, and the overall size of the device increases, impairing its significance as a power generation device.

  The present invention has been made to solve the above-described problems. According to some aspects of the present invention, a power generation device using the piezoelectric effect of a piezoelectric material, which can generate a high voltage with a small circuit scale, and has high power generation efficiency for generating power even with weak vibrations. Provide power generation equipment.

(1) The present invention is a power generation device, wherein a deformation member that is deformed by switching a deformation direction, a first piezoelectric element provided on the deformation member, and an alternating current generated by the first piezoelectric element A first rectifier circuit for rectification; an inductor constituting a resonance circuit including the first piezoelectric element; a first switch provided in the resonance circuit; and the first piezoelectric element provided in the deformable member. A second piezoelectric element having a higher output voltage than the second piezoelectric element, a second rectifier circuit that rectifies an alternating current generated by the second piezoelectric element, the first rectifier circuit, or the second rectifier circuit A storage element that performs charging based on an output signal, a control unit that controls the first switch, and a storage voltage detection circuit that detects a voltage of the storage element.

(2) In this power generation device, when it is determined that the first switch cannot be driven based on the voltage of the storage element detected by the storage voltage detection circuit, the storage element is based on the output voltage of the second piezoelectric element. May be charged.

(3) In the power generation device, a switching unit that is provided between the second piezoelectric element and the second rectifier circuit and switches a connection state between the second piezoelectric element and the second rectifier circuit. And the control means sets the switching unit in a non-conduction state based on the voltage of the storage element detected by the storage voltage detection circuit, detects the voltage of the second piezoelectric element, and sets the first switch to a predetermined state. It is good also as a period conduction state.

  In these inventions, since the first piezoelectric element and the second piezoelectric element are provided on the deformable member, the first piezoelectric element and the second piezoelectric element are also deformed when the deformable member is deformed. As a result, positive and negative charges are generated in these piezoelectric elements due to the piezoelectric effect. Further, the amount of generated charge increases as the deformation amount of the piezoelectric element increases. The first piezoelectric element forms a resonance circuit together with the inductor, and the resonance circuit is provided with a switch (first switch). Then, by making the first switch conductive at an appropriate timing, the control means can reverse the arrangement of the positive and negative charges generated in the first piezoelectric element, and it is necessary to prepare a booster circuit separately. A high voltage can be obtained with a small circuit scale.

  Here, an appropriate timing for turning on the first switch may be obtained by detecting the voltage of the second piezoelectric element. At this time, efficient power generation becomes possible. First, the deformation of the deformable member is started in a state where the conduction of the first switch is cut off, and the first switch is turned on when the deformation amount reaches 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 first switch is connected to form a resonance circuit, and then the first switch is disconnected when half the resonance period has elapsed, The arrangement of the positive and negative charges generated in the first piezoelectric element before connecting the inductor 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. Furthermore, in order to efficiently store charges in the first piezoelectric element in this way, it is important to connect the first switch to form a resonance circuit when the deformation direction of the first piezoelectric element is switched. Become. 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. From this, if the voltage generated in the second piezoelectric element is detected and the first switch is turned on only for a predetermined period from the time when the voltage has reached the extreme value, the first piezoelectric element is efficiently contained in the first piezoelectric element. Charges can be accumulated.

  Here, the power generation device according to these inventions includes a power storage element. Therefore, after the storage element is charged, the first switch can be driven using the storage element as a power source. However, for example, the first switch cannot be driven in a state where the storage element is discharged at the time of starting the power generation device. Further, when the externally applied vibration is weak and the deformation amount of the first piezoelectric element is not large, the output voltage of the first piezoelectric element does not reach the threshold voltage necessary for charging the storage element. there is a possibility. In such a case, if there is no auxiliary power supply or the like, efficient power generation performed by switching the first switch cannot be started. However, when the auxiliary power source is included in the power generation device, there arises a problem that the size of the entire device increases, and the significance as the power generation device is also lost.

  In the power generation devices according to these inventions, the output voltage of the second piezoelectric element is set higher than the output voltage of the first piezoelectric element in order to reliably charge the power storage element even when the operation is started. At this time, a switching unit that switches a connection state between the second piezoelectric element and the second rectifier circuit may be provided. It is preferable that the switching unit includes a switch that is normally on so that the second piezoelectric element and the second rectifier circuit are connected at the time of activation. When the first switch cannot be driven by the storage element, the storage element is charged by the second piezoelectric element having a high output voltage. At this time, the second piezoelectric element is used as a power generating piezoelectric element. In the power generation device according to these inventions, even when the output voltage of the first piezoelectric element does not reach the threshold voltage necessary for charging the power storage element, the power storage element is reliably charged by the second piezoelectric element. can do. Then, when charging progresses and the first switch can be driven by the power storage element, the voltage generated in the second piezoelectric element is detected, and the first switch is applied for a predetermined period from the time when the voltage becomes an extreme value. Is made conductive and charges are efficiently accumulated in the first piezoelectric element. During this normal operation, the switching unit is in a non-conduction state (a state in which the second piezoelectric element and the second rectifier circuit are not connected), and the second piezoelectric element gives the conduction timing of the first switch. Used as a piezoelectric element for control. As described above, the power generation devices according to these inventions can surely perform efficient power generation even with weak vibrations.

(4) In this power generation device, the capacitance of the second piezoelectric element may be smaller than the capacitance of the first piezoelectric element.

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

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

(7) In this power generation device, the deformable member may include a fixed end that does not deform, and the second piezoelectric element may be provided at a location closer to the fixed end than the first piezoelectric element. Good.

  According to these inventions, since the capacitance of the second piezoelectric element is smaller than the capacitance of the first piezoelectric element, the output voltage of the second piezoelectric element is made higher than the output voltage of the first piezoelectric element. Can also be high. In order to adjust the capacitance, the area of the electrode of the second piezoelectric element may be made smaller than the area of the electrode of the first piezoelectric element. Since the capacitance component of the piezoelectric element is reduced by reducing the area, the output voltage of the second piezoelectric element can be increased.

  In addition, the thickness of the piezoelectric member sandwiched between the pair of electrodes of the second piezoelectric element may be made thicker than the piezoelectric member sandwiched between the pair of electrodes of the first piezoelectric element. Since the capacitance component of the piezoelectric element is reduced by increasing the distance between the electrodes, the output voltage of the second piezoelectric element can be increased.

  At this time, if the first piezoelectric element and the second piezoelectric element are provided on the same surface of the deformable member, the installation area of the first piezoelectric element is reduced by the amount of the second piezoelectric element. Therefore, if the first piezoelectric element and the second piezoelectric element are provided on different surfaces of the deformable member, the installation area of the first piezoelectric element can be increased. Capability can be secured.

  On the other hand, if the first piezoelectric element and the second piezoelectric element are provided on the same surface of the deformable member, the first piezoelectric element and the second piezoelectric element are provided on the deformable member at the same time (in the same process). be able to. For this reason, it becomes possible to manufacture a power generator with high productivity.

  When the second piezoelectric element is provided on the same surface of the deformable member, the second piezoelectric element may be provided at a location closer to the fixed end of the deformable member than the first piezoelectric element. When installed near the fixed end of the deformable member, the output voltage can be increased because the deformation of the piezoelectric element is large.

(8) The present invention provides a deformable member that deforms by changing the deformation direction, a first piezoelectric element provided on the deformable member, and a first rectifier that rectifies an alternating current generated by the first piezoelectric element. A circuit, an inductor constituting a resonance circuit including the first piezoelectric element, a first switch provided in the resonance circuit, and an output voltage higher than that of the first piezoelectric element provided in the deformable member. Charging based on a second piezoelectric element, a second rectifier circuit that rectifies an alternating current generated by the second piezoelectric element, and an output signal from the first rectifier circuit or the second rectifier circuit And a storage voltage detection circuit that detects a voltage of the storage element, wherein the voltage of the storage element is determined based on an output signal from the storage voltage detection circuit. Step to compare with the threshold If, comprising the steps of: causing the charging based on the output voltage of the second piezoelectric element when it is determined that it can not drive the first switch, the electric storage device by the storage element.

  According to the present invention, when it is determined that the first switch cannot be driven by the storage element, the storage element is charged by the second piezoelectric element having a higher output voltage. Note that in the power generation device, a switching unit including a normally-on switch may be included between the second piezoelectric element and the power storage element.

  For this reason, even when the output voltage of the first piezoelectric element is low, the power storage element can be reliably charged. In other words, in the power generation device using the piezoelectric effect that can generate a high voltage with a small circuit scale, by performing the above-described control, an auxiliary power source or the like is unnecessary, and even a weak vibration is surely efficient. Power generation.

(9) The present invention is an electronic apparatus including the power generation device described above.

(10) The present invention is a moving means including any 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. Further, this moving means (for example, a vehicle, a train, etc.) can generate electric power by vibration accompanying the movement, and can efficiently supply power to, for example, equipment provided in the moving means.

It is explanatory drawing which showed the structure of the electric power generating apparatus of a present Example. 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 explanatory drawing which shows the reason why a switch is controllable at appropriate timing by detecting the voltage of the piezoelectric element for control. It is a figure which shows the mode of charge of the electrical storage element by a 2nd piezoelectric element. It is the flowchart which showed the control processing which switches ON / OFF of a switch. It is the flowchart which showed the 1st switch control process which switches ON / OFF of a 1st switch. It is explanatory drawing which showed the example of installation in case the 1st, 2nd piezoelectric element is provided in another surface of a beam. It is explanatory drawing which showed the example of installation in case the 1st, 2nd piezoelectric element is provided in the same surface of a beam.

Hereinafter, in order to clarify the contents of the present invention described above, examples will be described in the following order.
A. Structure of power generator:
B. Power generator operation (normal operation mode):
C. Operating principle of power generator (normal operation mode):
D. Switch switching timing:
D-1. First switch SW1 (normal operation mode):
D-2. Switching operation mode (from preparation operation mode to normal operation mode):
E. Example of piezoelectric element installation:
F. Other:

A. 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. In addition, a piezoelectric member 108 and a piezoelectric member 110 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 110 is provided with a first electrode 111a and a second electrode 111b formed of a metal thin film. The piezoelectric member 110, the first electrode 111a, and the second electrode 111b constitute a piezoelectric element (hereinafter referred to as a second piezoelectric element).

  In the example shown in FIG. 1A, the length of the piezoelectric member 110 (longitudinal direction of the beam 104) is shorter than that of the piezoelectric member 108. By adjusting the length, the capacitance component of the second piezoelectric element is reduced from that of the first piezoelectric element so that the amplitude of the output voltage of the second piezoelectric element is larger than that of the first piezoelectric element. As will be described later, the amplitude of the output voltage of the second piezoelectric element can be increased by a method other than the adjustment of the length. 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 110 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. Further, since the piezoelectric member 108 and the piezoelectric member 110 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 110 attached to the surface of the beam 104. Each of the piezoelectric member 108 and the piezoelectric member 110 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 110 is applied to the first electrode 111a and the second electrode. Appears on electrode 111b. 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 110 can also be represented as a current source and a capacitor Cs that stores electric charge. Among these, the piezoelectric member 108 is connected with an inductor L in parallel to form an electrical resonance circuit together with the capacitance component (capacitor Cg) of the piezoelectric member 108. A first switch SW1 for turning on / off the resonance circuit is provided in the resonance circuit (in series with the inductor L). ON / OFF of the first switch SW1 is controlled by a control circuit 112 (corresponding to control means). Here, the control circuit 112 of this embodiment includes a voltage detection circuit 124 and a switch control circuit 126. Then, the switch control circuit 126 controls ON / OFF of the first switch SW1. Details of each circuit will be described later.

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

  In addition, the first electrode 111a and the second electrode 111b provided on the piezoelectric member 110 pass through the second switch SW2 and the third switch SW3, respectively, and the second full-wave composed of four diodes D5 to D8. It is connected to a rectifier circuit 121 (corresponding to the second rectifier circuit). Second full-wave rectifier circuit 121 is connected to power storage element C <b> 1 in parallel with first full-wave rectifier circuit 120. The second switch SW2 and the third switch SW3 constitute a switching unit 113 that controls the connection between the second piezoelectric element and the second full-wave rectifier circuit 121.

  Here, the storage voltage detection circuit 125 detects the voltage of the storage element C1. If the voltage of the power storage element C1 is equal to or higher than the predetermined threshold value Vth, it is determined that the first switch SW1 can be driven using the power storage element C1 as a power source (hereinafter, a normal operation mode). If the voltage of the storage element C1 is less than the threshold value Vth, the storage voltage detection circuit 125 determines that the first switch SW1 cannot be driven using the storage element C1 as a power source (hereinafter, a preparation operation mode). Then, a signal corresponding to the normal operation mode or the preparation operation mode is output to the switch control circuit 126. The storage voltage detection circuit 125 may output a signal (high level or low level) according to the normal operation mode or the preparation operation mode by a comparator (comparator) with the threshold value Vth.

  The switch control circuit 126 controls ON / OFF of the first switch SW1, the second switch SW2, and the third switch SW3 in accordance with a signal representing the operation mode from the stored voltage detection circuit 125. In the preparation operation mode, the first switch SW1 cannot be turned ON / OFF. Here, in this embodiment, it is assumed that the second switch SW2 and the third switch SW3 are normally on. At this time, the second piezoelectric element functions as a piezoelectric element for power generation, and the storage element C1 is charged based on the output voltage of the second piezoelectric element. On the other hand, in the normal operation mode, the switch control circuit 126 performs control to turn on the first switch SW1 for a predetermined period. At this time, the switch control circuit 126 turns off the second switch SW2 and the third switch SW3 (OFF).

  In the normal operation mode, the second piezoelectric element functions as a control piezoelectric element that gives the timing to turn on the first switch SW1. The voltage detection circuit 124 obtains the peak (extreme value) of the output voltage of the second piezoelectric element, and changes the output signal to the switch control circuit 126 at that timing.

  As described above, in the normal operation mode, the first piezoelectric element functions as a “power generation piezoelectric element” and the second piezoelectric element functions as a “control piezoelectric element”, and in the preparation operation mode, the second piezoelectric element. Is made to function as “a piezoelectric element for power generation”. Further, the first switch SW1 to the third switch SW3 are also appropriately switched ON / OFF according to the operation mode. With these controls, the power generation apparatus of this embodiment can generate a high voltage with a small circuit scale (normal operation mode), and does not require an auxiliary power source or the like (preparation operation mode).

  Hereinafter, the operation in the normal operation mode will be described, and then the timing of switching between the preparation operation mode and the operation mode will be described.

B. Power generator operation (normal operation mode):
FIG. 2 is an explanatory diagram showing the operation in the normal operation mode of the power generation apparatus 100 of the present embodiment. FIG. 2A 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. 2B shows the state of current generated by the piezoelectric member 108 as a result of deformation of the beam 104 and the electromotive force generated inside the piezoelectric member 108 as a result. In FIG. 2B, 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 with reference to FIG. 1, the beam 104 is also provided with the piezoelectric member 110, and when the beam 104 is deformed, the piezoelectric member 110 is also deformed similarly to the piezoelectric member 108. Accordingly, the current Ipzt and the potential difference Vpzt shown in FIG. 2B are also generated inside the piezoelectric member 110 just like the piezoelectric member 108.

  As shown in FIGS. 2A and 2B, 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. The potential difference Vpzt in the positive direction can be 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 first full-wave rectifier circuit 120, that is, VC1 + 2Vf. For example, the electric charge generated thereafter can be taken out as a direct current and stored in the electric 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 first 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 first switch SW1 in FIG. 1 is kept OFF, charges can be stored in the power storage element C1 for the portion indicated by hatching in FIG. 2B.

  In the power generation apparatus 100 of the present embodiment, the first switch SW1 is turned on at the timing shown in FIG. Then, as shown in FIG. 2D, when 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) turns on the first switch SW1. A phenomenon appears as if it has shifted. For example, in the period B indicated as “B” in FIG. 2D, the voltage waveform Vpzt indicated by a 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. 2D, 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. 2D), 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.

  When the first switch SW1 shown in FIG. 2B is kept OFF and as shown in FIG. 2D, the first switch SW1 is turned ON at the timing when the deformation direction of the beam 104 is switched. As is clear from comparison with the case, in the power generation device 100 of the present embodiment, by turning on the first switch SW1 at an appropriate timing, it is possible to efficiently store charges in the power storage element C1. . Therefore, in order to turn on the first switch SW1 at an appropriate timing, the power generation apparatus 100 of the present embodiment is provided with a control piezoelectric member 110, detects the voltage of the piezoelectric member 110, and detects the first switch SW1. Is controlling. 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. 2D (a state in which no charge is stored in the storage element C1) and a period H in FIG. 2D (a state in which a little charge is stored in the 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. 2D 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.

C. Power generator operating principle (normal operation mode):
FIG. 3 is an explanatory diagram conceptually showing the first half of the operating principle of the power generation apparatus 100 of the present embodiment. FIG. 4 is an explanatory diagram conceptually showing the latter half of the operating principle of the power generation apparatus 100 of the present embodiment. 3 and 4 conceptually show the movement of charges in Cg (the capacitor of the piezoelectric member 108) when the first switch SW1 is turned on in accordance with the deformation of the piezoelectric member 108. FIG. FIG. 3A 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, 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 (see FIG. 3B)), the first switch SW1 is turned on.

  FIG. 3C shows a state immediately after the first switch SW1 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 first switch SW1 is turned on, the magnetic flux tends to increase due to the flow of electric charge, and thus back electromotive force is generated in a direction that prevents the increase of the magnetic flux (in other words, the 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. 3C, the back electromotive force generated in the inductor L in this way is represented by a hatched arrow. Since such back electromotive force is generated, even if the first switch SW1 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 change rate 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 being reduced (direction in which a current is to flow) (see FIG. 3E). 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. 3F shows a state where all the positive and negative charges generated by the deformation of the piezoelectric member 108 have moved.

  If the first switch SW1 is kept 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. 3B). The positive charge that has returned to the upper surface side of the piezoelectric member 108 thus moves again to the lower surface side as described above with reference to FIGS. 3B to 3F.

  As described above, if the first switch SW1 is turned on in a state where the electric charge is stored in Cg (the capacitor of the piezoelectric member 108) and the state is maintained, the current between the piezoelectric member 108 and the inductor L can be reduced. A kind of resonance phenomenon occurs in which the directions are alternately reversed. 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 turning on the first switch SW1 (the state shown in FIG. 3C) to the state shown in FIG. 3F is T / 2.

  Therefore, when T / 2 has elapsed since the first switch SW1 was turned on, the first switch SW1 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. 3A, the piezoelectric member 108 is deformed upward, but in FIG. 4A, it is deformed downward, so that 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. 3A to 3F, the piezoelectric member 108 (precisely, the beam 104) is not positively connected to the lower surface side of the piezoelectric member 108 at a stage 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. 4B 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 first switch SW1 turned off. Yes.

  When the first switch SW1 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 becomes the inductor. Try to flow to L. At this time, since a counter electromotive force is generated in the inductor L (see FIG. 4C), the current starts to flow little by little, but eventually reaches a peak, and then starts to decrease. 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. 4E). 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. 4 (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 first switch SW1 is turned on, when the time T / 2 has elapsed, the first switch SW1 is turned off, and this time, the piezoelectric member 108 (more precisely, the beam 104) faces upward (the upper surface side is concave). In this case, 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. 2, 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 first switch SW <b> 1 is turned on. That is, for example, in the period A shown in FIG. 2D, 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 first full-wave rectifier circuit 120, the charge in the portion exceeding the sum of VC1 and 2Vf is connected to the first full-wave rectifier circuit 120. Flow into the storage element C1. As a result, when the first switch SW1 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 via the inductor L, and the piezoelectric member The arrangement of positive and negative charges in 108 is interchanged. As apparent from the mechanism described above with reference to FIGS. 3 and 4, the period during which the first switch SW <b> 1 is ON is the resonance period of the resonance circuit configured by the capacitor of the piezoelectric member 108 and the inductor L. Half of the 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. 2D, 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 first switch SW1 is turned on for a half of 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 in the period C shown in FIG. 2D, 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. 2, 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. 2D, when the power storage element C1 is not charged, the voltage generated between the terminals of the piezoelectric member 108 is the first full-wave rectifier circuit. If it exceeds 2Vf of 120, the electric charge flows from the piezoelectric member 108 to the power storage element C1, so that 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. 3 and 4, 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.

D. Switch switching timing:
D-1. First switch SW1 (normal operation mode):
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 first switch SW1 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 first switch SW1 is set by detecting the voltage generated in the piezoelectric member 110. I have control.

  FIG. 5 is an explanatory diagram showing the reason why the first switch SW1 can be controlled at an appropriate timing by detecting the voltage generated in the piezoelectric member 110 for control. FIG. 5A shows the displacement of the beam 104. FIG. 5B 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. 3 and 4, when the first switch SW <b> 1 is turned on at the timing when the displacement of the beam 104 reaches the extreme value, it is possible to generate power most efficiently. As apparent from a comparison between FIG. 5A and FIG. 5B, 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 second switch SW2 and the third switch SW3 are in a non-conductive state in the normal operation mode), the increase / decrease in charge is the piezoelectric member 110. This is directly reflected in the change in the electromotive force Vpzt. 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. 5B, the timing at which the electromotive force Vpzt of the piezoelectric member 110 becomes an extreme value is detected, and from the timing, the time half the above-described resonance period (T / 2) If only the first switch SW1 is turned on, power can be generated efficiently.

D-2. Switching operation mode (from preparation operation mode to normal operation mode):
FIG. 6 shows the transition from the preparatory operation mode to the normal operation mode, and particularly shows the state of charging of the electricity storage element by the second piezoelectric element. Here, it is assumed that the preparatory operation mode is before time T1 in FIG. 6 and the normal operation mode is after time T1. For example, it is assumed that the first switch SW1 cannot be driven with the power storage element C1 as a power source before time T1 due to discharge or the like. Prior to time T1, for example, this corresponds to the state when the power generator is activated. At this time, as described above, the first switch SW1 cannot be turned on / off at a predetermined timing, and efficient power generation by the first piezoelectric element cannot be performed.

  FIG. 6A shows the output voltage Vgen (see FIG. 1B) of the first piezoelectric element. Since the first piezoelectric element is connected to the first full-wave rectifier circuit 120, only the charge that exceeds the sum of VC1 and 2Vf flows into the storage element C1. However, in the example of FIG. 6A, the vibration due to the external force is weak, indicating that the power storage element C1 is not charged by the output voltage Vgen of the first piezoelectric element before time T1.

  FIG. 6B shows the output voltage Vsen (see FIG. 1B) of the second piezoelectric element. Since the first piezoelectric element and the second piezoelectric element are provided on the same deformable member, the two piezoelectric elements are deformed in the same manner. However, when deformed in the same way, the second piezoelectric element outputs a higher voltage than the first piezoelectric element. Therefore, as shown in FIG. 6B, a portion (shaded line) exceeding the sum of VC1 and 2Vf occurs before time T1. Therefore, in the preparatory operation mode prior to time T1, the power storage element C1 can be charged using the second piezoelectric element as a power generation piezoelectric element.

  In this embodiment, the second piezoelectric element is connected to a second full-wave rectifier circuit 121 including four diodes D5 to D8 via a second switch SW2 and a third switch SW3, respectively. (See FIG. 1 (b)). Here, the second switch SW2 and the third switch SW3 are normally on. The second full-wave rectifier circuit 121 has the same configuration as the first full-wave rectifier circuit 120, and the diodes D5 to D8 correspond to the diodes D1 to D4, respectively.

  Then, in the preparatory operation mode (before time T1), the second piezoelectric element is connected to the second full-wave rectifier circuit 121, and the portion where the output voltage Vsen exceeds the sum of VC1 and 2Vf (hatched line) The generated charge is extracted as a direct current and stored in the storage element C1.

  VC1 in FIG. 6C is a voltage across the terminals of the storage element C1. In the preparation operation mode, it can be seen that VC1 is increased by the shaded portion in FIG. 6B. When VC1 reaches the threshold value Vth, the first switch SW1 can be driven using the power storage element C1 as a power source. Therefore, the normal operation mode is switched to enable efficient power generation by the first piezoelectric element (time T1). Or later).

  At this time, the comparison between VC1 and the threshold value Vth is performed by the storage voltage detection circuit 125 (see FIG. 1B), and the comparison result is transmitted to the switch control circuit 126. As shown in FIGS. 6D to 6E, the switch control circuit 126 maintains the conductive state of the second switch SW2 and the third switch SW3 that are normally on in the preparatory operation mode (before time T1). To do. When the mode is switched to the normal operation mode, the second switch SW2 and the third switch SW3 are turned off and the first switch SW1 is controlled to be turned on / off. Note that the operation in the normal operation mode has already been described in detail with reference to FIG. 2, and is omitted here for the sake of preventing duplicate description.

  FIG. 7 is a flowchart showing a control process when shifting to the preparation operation mode and the normal operation mode. This process is performed by the control circuit 112 (the voltage detection circuit 124 and the switch control circuit 126) except for the initialization of the switch. Note that the control circuit 112 may be a CPU.

  When the power generator is activated, the switch state is first initialized. Specifically, the first switch SW1 is turned off, and the second switch SW2 and the third switch SW3 are turned on (step S2). Note that the switch state may be initialized using a global reset signal or the like as a trigger.

  Then, based on the signal from the storage voltage detection circuit 125, the control circuit 112 determines whether or not the terminal voltage VC1 of the storage element C1 is equal to or higher than the threshold value Vth (step S4). If it is equal to or higher than the threshold value Vth (step S4: yes), the second switch SW2 and the third switch SW3 are turned off (step S6), and the “first switch control process (step S10)” which is the process in the normal operation mode is performed. Do. If it is less than the threshold value Vth (step S4: no), the second piezoelectric element is used as a power generation piezoelectric element in the preparatory operation mode and waits until the threshold value Vth is exceeded.

  FIG. 8 is a flowchart showing details of the first switch control process (step S10) in the normal operation mode. In the first switch control process, the electromotive force of the piezoelectric member 110 for control is detected, and the first switch SW1 is turned on / off.

  When the first 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 It is determined whether or not the value has reached an extreme value (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 first switch SW1 of the resonance circuit (resonance circuit constituted by the capacitor Cg and the inductor L of the piezoelectric member 108) is turned ON. (Step 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 first switch SW1 of the resonance circuit is turned off (step S108). Thereafter, the process returns to the top of the first switch control process, and the above-described series of processes is repeated.

  If the first switch SW1 of the resonance circuit is turned on / off as described above, the first switch SW1 can be easily turned on / off at an appropriate timing according to the movement of the beam 104. In this case, it is possible to efficiently generate power using the power generation device 100.

E. Example of piezoelectric element installation:
In the power generation apparatus 100 of the present embodiment described above, the first piezoelectric element and the second piezoelectric element are installed on the same deformable member. When the first switch SW1 is in a non-conductive state and the vibration is generated in the deformable member, the second piezoelectric element outputs a higher voltage than the first piezoelectric element. Here, the high voltage means that the amplitude of the output voltage is large (see FIGS. 6A and 6B).

  In order to make a difference in output voltage, the piezoelectric material may be changed between the first piezoelectric element and the second piezoelectric element. However, in consideration of the man-hours and costs at the time of manufacture, it is preferable to use the same piezoelectric material to make a difference in the output voltage level by means of installation. Therefore, an installation example in which the output voltage of the second piezoelectric element is higher than that of the first piezoelectric element even when the same piezoelectric material is used will be described below with reference to FIGS.

  FIG. 9 is an explanatory view showing an installation example in the case where the first piezoelectric element and the second piezoelectric element are provided on different surfaces of the beam 104. FIG. 9A is a plan view seen from one surface of the beam 104. FIG. 9B is a plan view seen from the other surface of the beam 104. FIG. 9A shows the piezoelectric member 108 and the first electrode 109 a provided on one surface of the beam 104. The piezoelectric member 108 and the first electrode 109a are components of the first piezoelectric element. FIG. 9B shows the piezoelectric member 110 and the second electrode 111 b provided on the other 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, since the first piezoelectric element and the second piezoelectric element are provided on different surfaces, the manufacturing process is somewhat complicated, but the first piezoelectric element used as a power generation piezoelectric element in the normal operation mode. The area of the element can be increased. As a result, the power generation capacity can be increased. In the installation example of the piezoelectric element shown in FIGS. 9A and 9B, the area of the surface where the second piezoelectric element is in contact with the beam 104 (corresponding to the deformable member) (“l2 *” in FIG. 9B). w2 ″) is smaller than the area of the surface where the first piezoelectric element is in contact with the beam 104 (“l1 * w1” in FIG. 9A). At this time, since the second electrode 109b of the first piezoelectric element and the first electrode 111a of the second piezoelectric element are in contact with the beam 104, the above area corresponds to the area of the electrode of each piezoelectric element.

  As described above, the piezoelectric member of the piezoelectric element can be expressed as a current source and a capacitor that stores electric charge. Assuming that the capacity of the capacitor is c, when charge Q is stored by charging, V = Q / c is established in relation to the voltage V (corresponding to the output voltage of the first and second piezoelectric elements). Therefore, the voltage V can be increased by reducing the capacitance c of the capacitor. Here, the capacitance c of the capacitor is expressed as c = εS / d using the dielectric constant ε, the distance d between the electrodes, and the area S of the electrodes. Therefore, V = Qd / (εS) holds. Therefore, the voltage V can be increased by making the area “l2 * w2” of the electrode of the second piezoelectric element smaller than the area “l1 * w1” of the electrode of the first piezoelectric element.

  Here, in addition to or instead of adjusting the area S of the electrodes (FIGS. 9A and 9B), the voltage V can be increased by adjusting the distance d between the electrodes. FIG. 9C shows the structure of the power generation device 100. Here, the distance between the electrodes of the first piezoelectric element is the thickness h1 of the piezoelectric member 108, and the distance between the electrodes of the second piezoelectric element is the thickness h2 of the piezoelectric member 110. At this time, there is a relationship of h1 <h2. Then, from the above formula (V = Qd / (εS)), the distance d between the electrodes is made larger in the second piezoelectric element, so that the voltage V can be increased.

  The second piezoelectric element can be charged in the preparatory operation mode by increasing the area of the first piezoelectric element as much as possible to improve the power generation capability in the normal operation mode by devising the installation of the piezoelectric element. The output voltage can be increased.

  Note that the second piezoelectric element is preferably installed as close to the support end 102 as possible. In a so-called cantilever beam such as the beam 104, the bending moment increases as it approaches the support end 102, and accordingly, the deformation amount of the beam 104 per unit length also increases. Therefore, the second piezoelectric element installed at a position close to the support end 102 is greatly deformed, and sufficient electric charges can be generated. At this time, since the charge Q does not need to be reduced by the above equation (V = Qd / (εS)), the voltage V can be effectively increased.

  FIG. 10 is an explanatory view showing an installation example in the case where the first piezoelectric element and the second piezoelectric element are provided on the same surface of the beam 104. If the first piezoelectric element and the second piezoelectric element are provided on the same surface of the deformable member, the installation area of the first piezoelectric element is reduced by the presence of the second piezoelectric element, and power generation in the normal operation mode is performed. It is disadvantageous in terms of ability. However, the first piezoelectric element and the second piezoelectric element can be provided on the deformable member in the same process at a time. For this reason, there exists an advantage that it becomes possible to manufacture an electric power generating apparatus with sufficient productivity.

  FIG. 10A is an installation example in the case where the first piezoelectric element and the second piezoelectric element are provided on the same surface of the beam 104, and is a plan view viewed from one surface of the beam 104. . In FIG. 10A, the width (longitudinal direction of the support end 102) and the length (longitudinal direction of the beam 104) of the piezoelectric member 110 of the second piezoelectric element are shorter than those of the piezoelectric member 108 of the first piezoelectric element. doing. Therefore, the area S of the electrode of the second piezoelectric element can be reduced and the voltage V can be increased (V = Qd / (εS)). The reason why the piezoelectric member 110 is installed at a position close to the support end 102 is to generate a sufficient charge Q, and the details are as described above.

  FIG. 10B is another installation example in the case where the first piezoelectric element and the second 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. . The piezoelectric member 110 of the second piezoelectric element has the same width as the piezoelectric member 108 of the first piezoelectric element, but is shorter than the piezoelectric member 108 of the first piezoelectric element. Then, the piezoelectric member 110 is placed near the support end 102 to generate a sufficient charge Q, and the area S is made smaller than that of the first piezoelectric element to increase the voltage V (V = Qd / (εS)). ).

  With such a device for installing the piezoelectric element, the second piezoelectric element is provided on the same surface of the beam 104 so that the power generation device can be manufactured with high productivity, and the second storage element can be charged in the preparatory operation mode. The output voltage of the piezoelectric element can be increased.

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

  For example, in the above-described embodiment, the piezoelectric member 108 has been described as being attached to the beam 104 having a cantilever structure. 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.

  In the present embodiment, the timing for turning on the first switch SW1 in the normal operation mode is determined based on the peak (extreme value) of the output voltage of the second piezoelectric element detected by the voltage detection circuit 124. However, for example, the current detection circuit may be used to detect when the current of the second piezoelectric element stops flowing, and the timing for turning on the first switch SW1 may be determined (see Ipzt in FIG. 2B). In addition, for example, a displacement sensor that directly measures the displacement of the deformable member may be used to detect when the displacement reaches a peak and determine the timing at which the first switch SW1 is turned on (see FIG. 2A). ). The displacement sensor may be, for example, a non-contact type eddy current sensor or an optical sensor.

  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).

  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 ... Electric power generation apparatus, 102 ... Support end, 104 ... Beam, 106 ... Weight, 108, 110 ... Piezoelectric member, 109a, 111a ... 1st electrode, 109b, 111b ... 2nd electrode, 112 ... Control circuit, 120 ... 1st Full wave rectifier circuit, 121 ... second full wave rectifier circuit, 124 ... voltage detection circuit, 125 ... storage voltage detection circuit, 126 ... switch control circuit, L ... inductor, C1 ... storage element, D1-D8 ... diode, SW1 ... 1st switch, SW2 ... 2nd switch, SW3 ... 3rd switch

Claims (9)

A deformable member that deforms by switching the deformation direction;
A first piezoelectric element provided on the deformable member;
A first rectifier circuit for rectifying an alternating current generated by the first piezoelectric element;
An inductor constituting a resonance circuit including the first piezoelectric element;
A first switch provided in the resonant circuit;
A second piezoelectric element provided on the deformable member and having an output voltage higher than that of the first piezoelectric element;
A second rectifier circuit for rectifying an alternating current generated by the second piezoelectric element;
A storage element that performs charging based on an output signal from the first rectifier circuit or the second rectifier circuit;
Control means for controlling the first switch;
A storage voltage detection circuit for detecting a voltage of the storage element ,
A power generation device that causes the storage element to charge based on the output voltage of the second piezoelectric element when it is determined that the first switch cannot be driven based on the voltage of the storage element detected by the storage voltage detection circuit . A deformable member that deforms by switching the deformation direction;
A first piezoelectric element provided on the deformable member;
A first rectifier circuit for rectifying an alternating current generated by the first piezoelectric element;
An inductor constituting a resonance circuit including the first piezoelectric element;
A first switch provided in the resonant circuit;
A second piezoelectric element provided on the deformable member and having an output voltage higher than that of the first piezoelectric element;
A second rectifier circuit for rectifying an alternating current generated by the second piezoelectric element;
A storage element that performs charging based on an output signal from the first rectifier circuit or the second rectifier circuit;
Control means for controlling the first switch;
A storage voltage detection circuit for detecting a voltage of the storage element;
A switching unit that is provided between the second piezoelectric element and the second rectifier circuit and switches a connection state between the second piezoelectric element and the second rectifier circuit;
The control means includes
Based on the voltage of the power storage element detected by the power storage voltage detection circuit, the switching unit is turned off, the voltage of the second piezoelectric element is detected, and the first switch is turned on for a predetermined period. . The power generator according to claim 1 or 2 ,
The electric power generating apparatus wherein the capacitance of the second piezoelectric element is smaller than the capacitance of the first piezoelectric element. In the electric power generating apparatus in any one of Claims 1 thru | or 3 ,
The power generation apparatus in which the first piezoelectric element and the second 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 3 ,
The first piezoelectric element and the second piezoelectric element are power generation devices provided on the same surface of the deformable member. The power generator according to claim 5 ,
The deformable member is
Consists of a fixed end that does not deform,
The second piezoelectric element is a power generation device provided at a location closer to the fixed end than the first piezoelectric element. A deformation member that deforms by switching a deformation direction, a first piezoelectric element provided on the deformation member, a first rectifier circuit that rectifies an alternating current generated by the first piezoelectric element, and the first An inductor constituting a resonance circuit including a piezoelectric element; a first switch provided in the resonance circuit; a second piezoelectric element provided in the deformable member and having an output voltage higher than that of the first piezoelectric element; A second rectifier circuit that rectifies an alternating current generated by the second piezoelectric element, a first accumulator circuit, or a storage element that performs charging based on an output signal from the second rectifier circuit; A storage voltage detection circuit that detects a voltage of a storage element, and a control method for a power generation device comprising:
Comparing the voltage of the storage element with a predetermined threshold based on an output signal from the storage voltage detection circuit;
And a step of causing the power storage element to charge based on the output voltage of the second piezoelectric element when it is determined that the first switch cannot be driven by the power storage element. Electronic equipment including a power generator according to any one of claims 1 to 6. Moving means including a power generating device according to any one of claims 1 to 6.

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