As a conventional vibration power generation device, an electrostatic induction vibration power generation device is known in which a charge is applied to one electrode of a variable capacitor and a charge is induced to the opposed other electrode by electrostatic induction. In the electrostatic induction vibration power generation device, when the electrostatic capacitance is increased or decreased, the inducted charge is changed, and the charge change is taken out as electric energy, thereby generating power (for example, see Patent Document 1).
FIG. 14 is a schematic cross-sectional view of a vibration power generator 10 as an example of the conventional electrostatic induction vibration power generator using an electret material (see FIG. 4 and page 10 to page 11 of Patent Document 1).
The vibration power generator 10 shown in FIG. 14 is provided with a first substrate 11 having a plurality of conductive surface regions 13 and a second substrate 16 having a plurality of electret material regions 15. The first substrate 11 and the second substrate 16 are disposed so as to be separated by a predetermined distance. The second substrate 16 including the electret material regions 15 is used as a fixed member. The first substrate 11 including the conductive surface regions 13 is coupled to fixed structures 17 by springs 19. One ends of the right and left springs 19 are connected to side surfaces of the first substrate 11, and the other ends thereof are connected to the fixed structures 17. By the springs 19, the first substrate 11 is capable of moving, for example, in the horizontal direction of FIG. 14 and returning to the home position. That is, the first substrate 11 is elastically supported by the right and left springs 19. By the first substrate 11 as a movable member moving with respect to the second substrate 16 as the fixed member, the area of the overlap between the electret material regions 15 and the opposed conductive surface regions 13, that is, the electrostatic capacitance is increased or decreased, so that a charge change occurs in the conductive surface regions 13. The electrostatic induction vibration power generator 10 generates power by taking out this charge change as electric energy.
Then, according to the frequency of the vibration used for power generation, the resonance frequency of the vibration of the first substrate 11 is selected.
Non-Patent Document 1 discloses an electrostatic induction vibration power generator similar to that of Patent Document 1. FIG. 15A is a perspective view of an electrostatic induction vibration power generator disclosed in Non-Patent Document 1. FIG. 15B is a cross-sectional view showing the electrode configuration.
A vibration power generator 20 is constituted by a first substrate 21 having a plurality of electret electrodes 23 and a second substrate 26 having a plurality of counter electrodes 25. The first substrate 21 and the second substrate 26 are disposed at a predetermined distance from each other. The second substrate 26 including the counter electrodes 25 is used as a fixed member. The first substrate 21 including the electret electrodes 23 is coupled to fixed structures 27 by right and left springs 29. One end portions of the springs 29 are connected to side surfaces of the first substrate 21, and the other end portions thereof are connected to the fixed structures 27. The operation of this vibration power generator 20 is similar to that of Patent Document 1.
As shown in FIG. 15B, the electret electrodes 23 and guard electrodes 28 are formed in strip form.