Piezoelectric micro-blower
A piezoelectric micro-blower capable of efficiently conveying compressive fluid without use of a check valve and ensuring a sufficient flow rate. The micro-blower has a blower body with a first wall and a second wall. Openings are formed in the respective walls and face a center of a diaphragm. An inflow path allowing the openings to communicate with the outside is formed between the walls. By applying a voltage to a piezoelectric element to cause the diaphragm to vibrate, a part of the first wall close to the first opening vibrates. Thus, gas can be drawn from the inflow path and discharged from the opening in the second wall.
1. A piezoelectric micro-blower comprising:
a blower body;
a diaphragm secured to the blower body at a perimeter thereof and including a piezoelectric element;
a first wall attached to the blower body and positioned so as to define a blower chamber between the diaphragm and the first wall, the first wall including a first opening facing a center of the diaphragm, the first opening being in fluid communication with the blower chamber;
a second wall spaced from the first wall and disposed opposite the blower chamber with the first wall interposed between the second wall and the blower chamber, the second wall including a second opening facing the first opening; and
an inflow path disposed between the first wall and the second wall, the inflow path including outer ends communicating with the outside of the piezoelectric micro-blower and inner ends connected to the first opening and the second opening; and
a center space disposed at the inner ends of the inflow path and having an opening area greater than an opening area of the first opening and an opening area of the second opening; wherein
the opening area of the center space is dimensioned such that a portion of the first wall facing the center space resonates in response to displacement of the diaphragm; and
the first wall does not include any piezoelectric elements.
2. The piezoelectric micro-blower according to claim 1 , wherein the inflow path includes a plurality of paths extending radially from the center space, each path including an outer end provided with an inlet.
3. The piezoelectric micro-blower according to claim 2 , wherein the outer end of each path opens on a different surface of the piezoelectric micro-blower than the second opening.
4. The piezoelectric micro-blower according to claim 1 , wherein the portion of the first wall facing the center space vibrates with a phase delay of about 90° relative to vibration of the diaphragm.
5. The piezoelectric micro-blower according to claim 1 , wherein the piezoelectric element is an annular piezoelectric element including a hollow at a center thereof.
6. The piezoelectric micro-blower according to claim 1 , wherein the diaphragm including the piezoelectric element is configured so as to be displaced in a first-order resonance mode or a third-order resonance mode when a voltage is applied to the piezoelectric element.
7. The piezoelectric micro-blower according to claim 1 , wherein the blower body includes:
a top plate defining the second wall;
a flow path plate;
a separator defining the first wall;
a blower frame; and
a bottom plate.
8. The piezoelectric micro-blower according to claim 7 , wherein the diaphragm is secured between the blower frame and the bottom plate.
9. The piezoelectric micro-blower according to claim 7 , wherein the flow path plate defines a center space, and the separator, the blower frame, the bottom plate and the diaphragm include notches at respective diagonal corners that form inlets to the center space.
10. The piezoelectric micro-blower according to claim 9 , wherein the bottom plate includes a slit.
11. The piezoelectric micro-blower according to claim 1 , further comprising an intermediate plate interposed between the diaphragm and the piezoelectric element.