US Patent No. 10,840,882

CRYSTAL UNIT AND MANUFACTURING METHOD THEREOF


Patent No. 10,840,882
Issue Date November 17, 2020
Title Crystal Unit And Manufacturing Method Thereof
Inventorship Koji Toshikawa, Saitama (JP)
Shinobu Yoshida, Saitama (JP)
Hirokazu Iwata, Saitama (JP)
Tetsuya Watanabe, Saitama (JP)
Kazuhiro Hirota, Saitama (JP)
Yoshiro Teshima, Saitama (JP)
Assignee NIHON DEMPA KOGYO CO., LTD., Tokyo (JP)

Claim of US Patent No. 10,840,882

1. A crystal unit comprisingan 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 depressed portion, the thick 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, and
the depressed portion is disposed from the thick portion toward a first end portion side, and a surface of the depressed portion is depressed with a predetermined angle ?a and subsequently bulged, and connected to the first end portion,
wherein when a dimension from an edge on a side of the first end portion of the thick portion to a distal end of the first end portion is defined as L, the L satisfies a following formula (1),
in the formula (1), n is an odd number, and ? is a wavelength of a flexure vibration that propagates along an X-axis of a crystal in the crystal unit,
L=?(n/4±0.25)  (1).