US Patent No. 10,771,038

CRYSTAL UNIT


Patent No. 10,771,038
Issue Date September 08, 2020
Title Crystal Unit
Inventorship Koji Toshikawa, Saitama (JP)
Shinobu Yoshida, Saitama (JP)
Hirokazu Iwata, Saitama (JP)
Assignee NIHON DEMPA KOGYO CO., LTD., Tokyo (JP)

Claim of US Patent No. 10,771,038

1. A crystal unit, comprising:an AT-cut crystal element that has a nearly-rectangular shape in a plan view and a part as a thick portion,
wherein
the AT-cut crystal element includes a first end portion, a first depressed portion, the thick portion, a second depressed portion, and a second end portion in this order from a side of one short side, in viewing a cross section taken along a longitudinal direction near a center of the short side of the AT-cut crystal element,
the first depressed portion is a depressed portion disposed from the thick portion toward a side of the first end portion, and a surface of the first depressed portion is depressed with a predetermined angle ?a and subsequently bulged, and connected to the first end portion,
the second depressed portion is a depressed portion disposed from the thick portion toward a side of the second end portion, and a surface of the second depressed portion is depressed with a predetermined angle ?b and subsequently bulged, and connected to the second end portion, and
when a dimension from a distal end of the first end portion to an edge on a side of the second depressed portion of the thick portion is defined as L, the L satisfies a following formula (1),
in the formula (1), n is a natural number, and ? is a wavelength of a flexure vibration that propagates along an X-axis of a crystal in the crystal unit,
L=?×(n/2±?)  (1).