Piezoelectric fan device and air-cooling apparatus using the piezoelectric fan device

Abstract

A piezoelectric fan device includes four piezoelectric fans that are arranged side-by-side in their width direction, and ends of the piezoelectric fans opposite to other ends in which the blades extend are coupled side-by-side and supported by a support. The piezoelectric fans include piezoelectric vibrators arranged to flexurally vibrate when a voltage is applied thereto and blades coupled to the piezoelectric vibrators such that the blades can be excited by the piezoelectric vibrators. Two central piezoelectric fans are driven in the same phase and the other two piezoelectric fans are driven in the opposite phase by a voltage applying device. Accordingly, not only vibrations of the centroid acting on the support but also moments about three axes are cancelled out.

1 . A piezoelectric fan device comprising:
 a plurality of piezoelectric fans arranged side-by-side in a width direction thereof, each of the plurality of piezoelectric fans including a piezoelectric vibrator and a blade, the piezoelectric vibrator being arranged to flexurally vibrate when a voltage is applied thereto, the blade being coupled to or integrally provided with the piezoelectric vibrator, the blade being arranged to be excited by the piezoelectric vibrator;   a support arranged to couple and support ends of the plurality of piezoelectric fans side-by-side, the ends being opposite to other ends from which the blades extend; and   a voltage applying device arranged to apply a voltage to each of the piezoelectric vibrators such that, with respect to a piezoelectric fan of the plurality of piezoelectric fans centrally located in the width direction or with respect to a gap between piezoelectric fans of the plurality of piezoelectric fans that are centrally located in the width direction, driving directions for the piezoelectric fans at both sides are axisymmetric and such that a driving direction for one half of the plurality of piezoelectric fans is in an opposite phase relative to a driving direction for a remaining one half of the plurality of piezoelectric fans.   
     
     
         2 . The piezoelectric fan device according to  claim 1 , wherein a number of the plurality of piezoelectric fans is a multiple of four. 
     
     
         3 . The piezoelectric fan device according to  claim 2 , wherein the piezoelectric fans are arranged side-by-side in a group or groups of four, two central piezoelectric fans are driven in the same phase, and two piezoelectric fans on both ends of the two central piezoelectric fans are driven in an opposite phase relative to the two central piezoelectric fans. 
     
     
         4 . The piezoelectric fan device according to  claim 1 , wherein
 each of the piezoelectric fans includes an elongated strip blade and a piezoelectric element fixed to an end of the elongate strip blade in a longitudinal direction thereof;   the end of the elongate strip blade in the longitudinal direction and the piezoelectric element define the piezoelectric vibrator; and   the end of the elongate strip blade in the longitudinal direction is coupled and supported by the support.   
     
     
         5 . The piezoelectric fan device according to  claim 1 , wherein each of the piezoelectric vibrators includes a first vibrator and a second vibrator, a first end of the first vibrator and a first end of the second vibrator in longitudinal directions thereof are coupled together, a second end of the first vibrator in the longitudinal direction thereof is coupled to the blade, a second end of the second vibrator in the longitudinal direction thereof is supported by the support, and the voltage applying device is connected so as to enable the first vibrator and the second vibrator to flexurally vibrate in opposite directions. 
     
     
         6 . An air-cooling apparatus in which the piezoelectric fan device according to  claim 1  is arranged in the vicinity of a heat sink that includes a plurality of dissipating fins spaced apart and arranged side-by-side and the blades are disposed in gaps between the dissipating fins such that directions in which the blades are displaced are parallel or substantially parallel to sides of the dissipating fins.