Piezoelectric Pump

Abstract

A piezoelectric pump having a first opening in a center portion of a pump body, and a second opening apart from the center. An outer peripheral portion of a metal diaphragm is fixed to the pump body, and a piezoelectric element having a size that covers the first opening and does not cover the second opening is bonded to a back center portion of the diaphragm. By applying a voltage near the resonance frequency to the piezoelectric element, a portion of the diaphragm opposing the first opening and a portion of the diaphragm opposing the second opening are bent in opposite directions so that fluid is drawn in from one of the first opening and the second opening and is discharged from the other opening. Such a piezoelectric pump can increase the discharging pressure, and can reliably discharge the fluid even under a condition where the pressure on the discharging side is high.

1 . A piezoelectric pump comprising:
 a pump body;   a diaphragm fixed at an outer peripheral portion thereof to the pump body;   a piezoelectric element bonded to a center portion of the diaphragm;   a first opening provided in a portion of the pump body opposing the center portion of the diaphragm; and   a second opening provided in one of (1) an intermediate region between the center portion and the outer peripheral portion of the diaphragm and (2) in a portion of the pump body opposing the intermediate region,   wherein the piezoelectric element is sized so as to cover the first opening and not cover the second opening, and   wherein a portion of the diaphragm opposing the first opening and a portion of the diaphragm opposing the second opening are bent in opposite directions when a voltage having a predetermined frequency to the piezoelectric element is applied so that fluid is drawn in from one of the first opening and the second opening and is discharged from the other of the first opening and the second opening.   
   
   
       2 . The piezoelectric pump according to  claim 1 , wherein the diaphragm is a metal plate. 
   
   
       3 . The piezoelectric pump according to  claim 1 , wherein the fluid is compressible fluid, and the fluid is drawn in from the first opening and is discharged from the second opening. 
   
   
       4 . The piezoelectric pump according to  claim 3 , wherein the fluid is drawn in from the first opening and is discharged from the second opening when a voltage near a primary resonance frequency of a displacement member defined by the diaphragm and the piezoelectric element is applied to the piezoelectric element. 
   
   
       5 . The piezoelectric pump according to  claim 1 , wherein the fluid is compressible fluid, and the fluid is drawn in from the second opening and is discharged from the first opening by applying a voltage near a tertiary resonance frequency of a displacement member defined by the diaphragm and the piezoelectric element to the piezoelectric element. 
   
   
       6 . The piezoelectric pump according to  claim 5 , wherein the fluid is drawn in from the second opening and is discharged from the first opening when a voltage near a tertiary resonance frequency of a displacement member defined by the diaphragm and the piezoelectric element is applied to the piezoelectric element. 
   
   
       7 . The piezoelectric pump according to  claim 5 , wherein the second opening is provided at a position where the diaphragm is maximally displaced. 
   
   
       8 . The piezoelectric pump according to  claim 5 , wherein the second opening is provided outside of a position where the diaphragm is maximally displaced. 
   
   
       9 . The piezoelectric pump according to  claim 1 , wherein a plurality of the second openings are provided on a common circumference centered on the first opening. 
   
   
       10 . The piezoelectric pump according to  claim 1 , further comprising a presser plate attached to the diaphragm on a side thereof that the piezoelectric element is bonded. 
   
   
       11 . The piezoelectric pump according to  claim 1 , wherein the diaphragm includes a plurality of arc-shaped slits. 
   
   
       12 . The piezoelectric pump according to  claim 1 , wherein the pump body includes an extending portion that extends outward from an outer peripheral portion of the diaphragm, and the second opening is provided on the extending portion so as to extend from an inner side of the outer peripheral portion to an outer side of the diaphragm. 
   
   
       13 . The piezoelectric pump according to  claim 12 , wherein an inner edge of the second opening is provided outside an outer periphery of the piezoelectric element and inside the outer peripheral portion of the diaphragm. 
   
   
       14 . The piezoelectric pump according to  claim 13 , wherein, an outer edge of the second opening is open on the extending portion. 
   
   
       15 . The piezoelectric pump according to  claim 1 , wherein the second opening is a hole extending through the pump body. 
   
   
       16 . The piezoelectric pump according to  claim 15 , wherein the second opening is arc-shaped. 
   
   
       17 . A piezoelectric pump comprising:
 a pump body;   a diaphragm fixed at an outer peripheral portion thereof to the pump body;   a piezoelectric element bonded to a center portion of the diaphragm;   a first opening provided in a portion of the pump body opposing the center portion of the diaphragm; and   a second opening provided in a portion of the pump body opposing an intermediate region between the center portion and the outer peripheral portion of the diaphragm,   wherein the piezoelectric element is sized so as to cover the first opening and not cover the second opening.   
   
   
       18 . The piezoelectric pump according to  claim 17 , wherein a plurality of the second openings are provided on a common circumference centered on the first opening. 
   
   
       19 . A piezoelectric pump comprising:
 a pump body;   a diaphragm fixed at an outer peripheral portion thereof to the pump body;   a piezoelectric element bonded to a center portion of the diaphragm;   a first opening provided in a portion of the pump body opposing the center portion of the diaphragm; and   a second opening provided in the diaphragm in an intermediate region between the center portion and the outer peripheral portion of the diaphragm,   wherein the piezoelectric element is sized so as to cover the first opening and not cover the second opening.   
   
   
       20 . The piezoelectric pump according to  claim 19 , wherein a plurality of the second openings are provided on a common circumference centered on the first opening.