Piezoelectric device
A piezoelectric device includes a connection section including a first coupling portion, a second coupling portion, and a bridging portion. The first coupling portion extends along a slit and is connected to one of a pair of beam sections. The second coupling portion extends along the slit and is connected to another of the pair of beam sections. The bridging portion is located between the slit and an opening and is connected to both of the first coupling portion and the second coupling portion. The beam sections are connected to each other in a circumferential direction of a base having an annular shape via the connecting section while each of the beam sections is interposed between the slits extending in intersecting directions.
1 . A piezoelectric device comprising:
a base having an annular shape;
a plurality of beam sections each of which includes a fixed end portion connected to the base and a tip end portion located on a side opposite to the fixed end portion and extends from the fixed end portion toward the tip end portion; and
a connecting section that connects, among the plurality of beam sections, a pair of beam sections adjacent to each other in a circumferential direction of the base; wherein
each of the plurality of beam sections is a piezoelectric vibrating section including a plurality of layers;
a slit defined by portions of a pair of end edges of adjacent ones of the pair of beam sections and an opening located adjacent to the tip end portions of the pair of beam sections while the opening is spaced apart from the slit and defined by other portions of the pair of end edges are provided between the pair of beam sections;
the connecting section is provided to fold back between the pair of beam sections;
the connecting section includes a first coupling portion extending along the slit and connected to one of the pair of beam sections, a second coupling portion extending along the slit and connected to another of the pair of beam sections, and a bridging portion located between the slit and the opening and connected to both of the first coupling portion and the second coupling portion; and
the plurality of beam sections are connected to each other in the circumferential direction via the connecting section while each of the plurality of beam sections is interposed between slits extending in intersecting directions.
2 . The piezoelectric device according to claim 1 , further comprising an outer peripheral slit extending along each of the first coupling portion and the second coupling portion at a distance from the slit and communicating with the opening.
3 . The piezoelectric device according to claim 1 , wherein
the plurality of layers include:
a piezoelectric layer made of a single crystal piezoelectric material;
a first electrode layer located on one side of the piezoelectric layer in a laminating direction of the layers; and
a second electrode layer located on another side of the piezoelectric layer to oppose at least a portion of the first electrode layer with the piezoelectric layer in between; and
an axial direction of a virtual axis when a polarization axis of the single crystal piezoelectric material is projected from the laminating direction onto a virtual plane orthogonal or substantially orthogonal to the laminating direction extends in a same direction in all of the plurality of beam sections and intersects an extending direction of each of the plurality of beam sections when viewed from the laminating direction.
4 . The piezoelectric device according to claim 3 , wherein an angle defined by the axial direction of the virtual axis and the extending direction of each of the plurality of beam sections when viewed from the laminating direction is about 40 degrees or more and about 50 degrees or less, or about 130 degrees or more and about 140 degrees or less.
5 . The piezoelectric device according to claim 3 , wherein the piezoelectric layer is made of lithium niobate (LiNbO 3 ) or lithium tantalate (LiTaO 3 ).
6 . The piezoelectric device according to claim 1 , wherein
the plurality of beam sections include four beam sections;
the fixed end portions of the four beam sections are located to define a square when viewed from a laminating direction; and
when viewed from the laminating direction, a ratio of a dimension of an extension length of each of the first coupling portion and the second coupling portion to a dimension of a shortest distance between the fixed end portions opposing each other among the fixed end portions of the four beam sections is about 32% or less.
7 . The piezoelectric device according to claim 1 , wherein a dimension of a minimum width of each of the first coupling portion and the second coupling portion is larger than a dimension of a thickness of each of the first coupling portion and the second coupling portion in a laminating direction.
8 . The piezoelectric device according to claim 6 , wherein the connecting section includes four connecting sections.
9 . The piezoelectric device according to claim 1 , wherein the plurality of beam sections are rotationally symmetric around a center of the base.
10 . The piezoelectric device according to claim 1 , wherein a total length of each of the plurality of beam sections in an extending direction is at least five times or more than a total thickness of each of the plurality of beam sections in a laminating direction.
11 . The piezoelectric device according to claim 3 , wherein a total width of the slit when viewed from the laminating direction is about 10 μm or less.
12 . The piezoelectric device according to claim 1 , wherein total lengths of the first coupling portion and the second coupling portion are about 10 μm or more and about 200 μm or less.
13 . The piezoelectric device according to claim 1 , wherein a side surface of the bridging portion which is in contact with the opening is curved.
14 . The piezoelectric device according to claim 3 , wherein a total thickness of each of the first electrode layer and the second electrode layer is about 0.05 μm or more and about 0.2 μm or less.
15 . The piezoelectric device according to claim 1 , wherein a hole is provided in the base adjacent to the opening.
16 . The piezoelectric device according to claim 1 , wherein each of the plurality of beam sections has a same or substantially a same resonant frequency.
17 . The piezoelectric device according to claim 1 , wherein each of the plurality of beam sections and the connecting section have the same or substantially the same thicknesses, hardness, and density.
18 . The piezoelectric device according to claim 1 , wherein the bridging portion has a semicircular shape with a radius centered at the slit.
19 . The piezoelectric device according to claim 1 , wherein a circular opening is provided at a tip of the slit.
20 . The piezoelectric device according to claim 19 , wherein a diameter of the circular opening is larger than a width of the slit.