Piezoelectric microvalve

1. A piezoelectric microvalve comprising:

an inlet plenum;

a flow directing structure for directing a fluid flow, a first side of the structure in fluid communication with the inlet plenum;

a piezoelectric bending actuator comprising a plurality of independently controllable flap portions extending from an attachment portion responsive to a command signal for controlling a fluid flow through the flow directing structure; and

an outlet plenum in fluid communication with a second side of the flow directing structure.

2. The microvalve of claim 1 , wherein the flow directing structure defines at least one orifice for directing the fluid flow.

3. The microvalve of claim 1 , wherein the flow directing structure comprises an elongated slot for directing the fluid flow.

4. The microvalve of claim 3 , the piezoelectric bending actuator further comprising a flap portion periphery greater than a slot periphery.

5. The microvalve of claim 3 , wherein the flap portion is positionable over the slot to alternately seal and unseal the slot.

6. The microvalve of claim 1 , the piezoelectric bending actuator further comprising:

a piezoelectric layer;

a first electrode layer positioned adjacent one side of the piezoelectric layer;

a second electrode layer positioned adjacent an opposite side of the piezoelectric layer; and

a backing layer attached to at least one side of the piezoelectric layer.

7. The microvalve of claim 6 , further comprising a polymer layer attached to a side of the piezo electric bending actuator facing the flow directing structure.

8. The microvalve of claim 6 , the piezoelectric layer further comprising a plurality of piezoceramic members held spaced apart by a plurality of spacing members.

9. The microvalve of claim 8 , wherein a size ratio between the piezoceramic members and the spacing members is selected to achieve a desired stiffness of the structure.

10. The microvalve of claim 6 , the piezoelectric layer further comprising a plurality of piezoceramic members held spaced apart in a polymer matrix.

11. The microvalve of claim 6 , wherein the first electrode layer comprises a positive electrode comprising a first set of spaced apart electrode fingers extending in direction perpendicular to a longitudinal axis of the piezoelectric bending actuator and a first negative electrode having a second set of spaced apart electrode fingers extending in direction perpendicular to the longitudinal axis and interdigitated with the first set of fingers.

12. The microvalve of claim 6 , wherein the second electrode layer comprises a second positive electrode comprising a third set of spaced apart fingers extending in direction perpendicular to the longitudinal axis, and a second negatively charged electrode having a fourth set of spaced apart fingers extending in direction perpendicular to the longitudinal axis and interdigitated with the third set of fingers, the second positive electrode layer vertically aligned with the first electrode layer.

13. The microvalve of claim 1 , in combination with a cooking appliance.

14. A method of controlling a fluid flow through a piezoelectric microvalve comprising:

providing an inlet plenum and an outlet plenum;

providing a flow directing structure in fluid communication between the inlet plenum and outlet plenum;

placing a piezoelectric bending actuator, comprising a plurality of independently controllable flap portions extending from an attachment portion responsive to a command signal for controlling a fluid flow; and

bending independently, in response to the command signal, the flap portions of the actuator to allow a fluid flowing from the inlet plenum to flow to the outlet plenum.

15. A piezoelectric microvalve comprising:

an inlet plenum;

a flow directing structure for directing a fluid flow, a first side of the structure in fluid communication with the inlet plenum;

a piezoelectric bending actuator comprising a flap portion responsive to a command signal for controlling a fluid flow through the flow directing structure and further comprising a plurality of piezoceramic members held spaced apart in a polymer matrix; and

an outlet plenum in fluid communication with a second side of the flow directing structure.

16. The microvalve of claim 15 , the piezoelectric bending actuator further comprising:

a piezoelectric layer;

a first electrode layer positioned adjacent one side of the piezoelectric layer;

a second electrode layer positioned adjacent an opposite side of the piezoelectric layer; and

a backing layer attached to at least one side of the piezoelectric layer.

17. The microvalve of claim 16 , wherein the first electrode layer comprises a positive electrode comprising a first set of spaced apart electrode fingers extending in direction perpendicular to a longitudinal axis of the piezoelectric bending actuator and a first negative electrode having a second set of spaced apart electrode fingers extending in direction perpendicular to the longitudinal axis and interdigitated with the first set of fingers.

18. The microvalve of claim 16 , wherein the second electrode layer comprises a second positive electrode comprising a third set of spaced apart fingers extending in direction perpendicular to the longitudinal axis, and a second negatively charged electrode having a fourth set of spaced apart fingers extending in direction perpendicular to the longitudinal axis and interdigitated with the third set of fingers, the second positive electrode layer vertically aligned with the first electrode layer.