Abstract:
A power generator includes a first terminal; a second terminal surrounding the first terminal; piezoelectric elements disposed radially around the terminals, one end of each element being connected to the terminals; and masses connected to the other ends of the elements.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application is based on, and claims priority to, Korean Application Serial Number 10-2006-0122827, filed on Dec. 6, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety. 
   FIELD OF THE INVENTION 
   The present invention relates to power generators using a piezoelectric material. 
   BACKGROUND OF THE INVENTION 
   The number of electronic parts in vehicles is increasing. The electronic parts are supplied with power from the vehicle battery. Therefore, many electric lines are necessary. 
   Recently, to reduce the number of electric lines, electronic parts including independent power generators have been provided. Such a power generator uses a piezoelectric material, and should have increased durability and generate a large amount of power using small vibrations. 
   SUMMARY OF THE INVENTION 
   Embodiments of the present invention provide a power generator, including a first terminal; a second terminal surrounding the first terminal; piezoelectric elements disposed radially around the terminals, one end of each element being connected to the terminals; and masses connected to the other ends of the elements. 
   The generator may further include a case, with receivers in which the masses are housed. The receivers restrict movement of the masses when vibration is applied thereto. 
   The first terminal may be connected to surfaces of the piezoelectric elements that generate a positive voltage, and may supply the positive voltage to an external electronic device. The second terminal may be connected to surfaces of the piezoelectric elements that generate a negative voltage, and may supply the negative voltage to the external electronic device. The terminals may each include a contact surface that is in contact with the external electronic device, and a contact bar that is in contact with the piezoelectric elements. The contact surface may be wider than the contact bar. 
   The piezoelectric elements may each include several piezoelectric sub-elements, connected in series or in parallel. 
   The generator may further include a diode that converts a positive/negative AC voltage from the terminals into a positive AC voltage, and a capacitor and a Zener diode that convert the positive AC voltage to a DC voltage. The capacitor may convert the positive AC voltage to a DC voltage in the a range of 0 to 50 V, and the Zener diode may convert the positive AC voltage output to a DC voltage in the range of 0 to 36 V. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the nature and objects of the present invention, reference should be made to the following detailed description with the accompanying drawings, in which: 
       FIG. 1A  is a plan view of a power generator using a piezoelectric material according to an embodiment of this invention; 
       FIG. 1B  is a perspective view of the power generator of  FIG. 1A ; 
       FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1B ; 
       FIG. 3A  is a schematic view showing a piezoelectric element in which piezoelectric sub-elements are connected in series; 
       FIG. 3B  is a schematic view showing a piezoelectric element in which piezoelectric sub-elements are connected in parallel; 
       FIG. 4  is a graph illustrating voltage generated by a power generator according to an embodiment of this invention; and 
       FIG. 5  is a view illustrating an exemplary device for converting an AC voltage, generated by the power generator according to an embodiment of this invention, into a DC voltage. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1A and 1B , a power generator using the piezoelectric material according to an embodiment of this invention includes an anode terminal  102 , a cathode terminal  104  that is disconnected from anode terminal  102  and surrounds anode terminal  102 , a plurality of piezoelectric elements  100  extending radially from anode terminal  102  and cathode terminal  104 , mass bodies  106  connected to ends of piezoelectric elements  100 , and a case  110  having receivers  108  in which mass bodies  106  are received. 
   Anode terminal  102  is connected to surfaces of piezoelectric elements  100  that generate a positive voltage, and is supplied with the positive voltage from piezoelectric elements  100 , and supplies the positive voltage to an external electronic device (not shown). Cathode terminal  104  is connected to surfaces of piezoelectric elements  100  that generate a negative voltage, and is supplied with the negative voltage from piezoelectric elements  100 , and supplies the negative voltage to the external electronic device (not shown). Referring to  FIG. 2 , a contact surface  102   a  of anode terminal  102  is in contact with an anode terminal of the external electronic device, and is wider than a contact bar  102   b  that is in contact with piezoelectric elements  100 , in order to facilitate the connection with the anode terminal of the external electronic device. A contact surface  104   a  of cathode terminal  104  is in contact with a cathode terminal of the external electronic device, and is wider than a contact bar  104   b  that is in contact with piezoelectric elements  100 , in order to facilitate the connection with the cathode terminal of the external electronic device. 
   When external vibrations are applied to piezoelectric elements  100 , piezoelectric elements  100  deform in all directions from anode terminal  102  and cathode terminal  104  in case  110 , and generate power. 
   Mass bodies  106  move by the external vibration to increase the deformation of piezoelectric elements  100 . Receivers  108  restrict the movement of mass bodies  106  to prevent damage to piezoelectric elements  100  due to the large deformation. Because of the mass bodies  106 , the power generator generates a large amount of power using small vibrations. Further, the radial arrangement of piezoelectric elements  100  and receiver  108  provide improved durability. 
   Each piezoelectric element  100  may be configured such that piezoelectric sub-elements  100   a  are connected in series to each other in a pole forming direction as shown in  FIG. 3A  or are connected in parallel to each other in the pole forming direction as shown in  FIG. 3B . A piezoelectric element  100  (see  FIG. 3A ) with piezoelectric sub-elements  100   a  being connected in series generates more power than a piezoelectric element  100  (see  FIG. 3B ) with piezoelectric sub-elements  100   a  being connected in parallel. Further, resonance frequency of piezoelectric elements  100  can be adjusted by adjusting the width, thickness, length, etc. of piezoelectric elements  100 . 
     FIG. 4  is a graph illustrating a voltage generated from the power generator using four 100 Hz piezoelectric elements and four 180 Hz piezoelectric elements. Referring to  FIG. 4 , the power generator according to one embodiment of this invention largely resonates at 100 Hz and 180 Hz, and more power is generated at 100 Hz and 180 Hz. It should be understood that when three different load resistors are connected to the power generator, the power supply varies depending on the types of the load resistors. 
   Referring to  FIG. 5 , a device for converting AC voltage generated by the power generator into a DC voltage includes a diode  120  that converts positive and negative AC voltage generated from anode terminal  102  and cathode terminal  104  into positive AC voltage, and a capacitor  130  and a Zener diode  140  that convert the positive AC voltage output from diode  120  into DC voltage. Capacitor  130  converts the positive AC voltage output from diode  120  into a DC voltage in the range of 0 to 50 V, and Zener diode  140  converts the positive AC voltage output from diode  120  into a DC voltage in the range of 0 to 36 V. 
   While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.