Piezoelectric actuator and pump using same

Abstract

A method of manufacturing piezoelectric actuators ( 14 ) is disclosed along with a miniature diaphragm pump ( 10 ) using the actuators. The object was an actuator which could be used in miniature diaphragm pumps and other applications and which would be smaller in size and simpler to manufacture than prior art actuators, yet would provide forces and displacements an order of magnitude higher than any previously known devices of similar size. The pump ( 10 ) incorporates the new actuator along with a novel one-way valve ( 200 ) and a small driver circuit ( 18 ). The pump is of direct application in the liquid cooling systems of small computers, and in other fluid systems.

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       29 . A piezoelectric actuator comprising: 
 a first metallic layer;    a piezoelectric element having a first surface adhered to the first metallic layer, the piezoelectric element also having a second surface which is opposite the first surface;    a second metallic layer adhered to the second surface of the piezoelectric element;    wherein a ratio of thickness of the first metallic layer to thickness the second metallic layer is about 2:1.    
   
   
       30 . The apparatus of  claim 29 , wherein the first metallic layer is stainless steel and the second metallic layer is aluminum.  
   
   
       31 . The apparatus of  claim 29 , wherein a ratio of thickness of the piezoelectric element to thickness of the first metallic layer is about 2:1.  
   
   
       32 . The apparatus of  claim 29 , wherein the first metallic layer has a greater surface area than the piezoelectric element and the piezoelectric element has a greater surface area than the second metallic layer.  
   
   
       33 . The apparatus of  claim 29 , wherein the first metallic layer has a greater diameter than the piezoelectric element and the piezoelectric element has a greater diameter than the second metallic layer.  
   
   
       34 . The apparatus of  claim 29 , wherein the first surface of the piezoelectric element is adhered to the first metallic layer by a polyimide adhesive, and wherein the second metallic layer is adhered to the second surface of the piezoelectric element by the polyimide adhesive.  
   
   
       35 . A pump comprising: 
 a body for at least partially defining a pumping chamber;    at least one piezoelectric actuator which, during application of an electric field, acts upon a fluid in the pumping chamber, the piezoelectric actuator comprising a first metallic layer secured to a first surface of the piezoelectric element and a second metallic layer secured to a second surface of the piezoelectric element, the second surface being opposite the first surface;    wherein the first metallic layer has a larger surface area than the piezoelectric element so that the piezoelectric element is setback from an edge of the first metallic layer;    wherein the piezoelectric element is substantially enclosed between the first metallic layer and the second metallic layer except insofar as the second metallic layer is setback from an edge of the piezoelectric element in view of the second metallic layer having a smaller surface area than the piezoelectric element;    wherein the first metallic layer has a rim which serves as a clamping surface for clamping the piezoelectric actuator in position within the body.    
   
   
       36 . The apparatus of  claim 35 , wherein the second metallic layer does not serve to clamp the piezoelectric actuator in position within the body.  
   
   
       37 . The apparatus of  claim 35 , wherein the piezoelectric element comprises a polycrystalline material.  
   
   
       38 . The apparatus of  claim 35 , wherein the first metallic layer comprises stainless steel.  
   
   
       39 . The apparatus of  claim 35 , wherein the piezoelectric actuator further comprises a polyimide adhesive which adheres at least one of (1) a first surface of the piezoelectric element to the first metallic layer; and (2) a second surface of the piezoelectric element to the second metallic layer.  
   
   
       40 . The apparatus of  claim 35 , wherein the second metallic layer comprises aluminum.  
   
   
       41 . The apparatus of  claim 35 , wherein relative sizes of the surface area of the second metallic layer and the piezoelectric element are chosen to prevent arcing over of a driving voltage from the second metallic layer to the first metallic layer.  
   
   
       42 . The apparatus of  claim 35 , wherein the body has a port which is situated so that fluid traveling between the port and the pumping chamber travels in a direction parallel to a plane of the piezoelectric actuator.  
   
   
       43 . The apparatus of  claim 35 , wherein the body has a port which is situated so that fluid traveling between the port and the pumping chamber travels in a direction perpendicular to a plane of the piezoelectric actuator.  
   
   
       44 . The apparatus of  claim 35 , further comprising a second piezoelectric actuator which is situated in mirror image positioning to the at least one piezoelectric actuator with respect to the pumping chamber.  
   
   
       45 . The apparatus of  claim 35 , further comprising a sealing member which provides a seal between the piezoelectric actuator and the body and which defines a thickness of the pumping chamber, the thickness of the pumping chamber facilitating self-priming of the pump.  
   
   
       46 . The apparatus of  claim 35 , wherein the piezoelectric actuator is substantially unconstrained in its placement in the body except by being secured to the first metallic layer.  
   
   
       47 . The apparatus of  claim 35 , wherein the piezoelectric actuator has mechanical contact with the body only through the rim of the first metallic layer.