# US 10,771,038 B2 · Crystal unit

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- Number: US 10,771,038 B2
- Document ID: US10771038B2
- Status: Granted
- Kind: B2
- Application number: 16/391,330
- Filed: 2019-04-23
- Published: 2019-10-24
- Granted: 2020-09-08
- Earliest claimed: 2018-04-24
- Assignees: Nihon Dempa Kogyo Co., Ltd.
- Applicants: Nihon Dempa Kogyo Co., Ltd.
- Inventors: Koji Toshikawa; Shinobu Yoshida; Hirokazu Iwata
- Web page: https://patentgrep.com/patent/US10771038B2

## CPC

- H03H 9/02023: {consisting of quartz}
- H03B 5/32: being a piezoelectric resonator (selection of piezoelectric material H10N30/00)
- H03H 3/02: for the manufacture of piezoelectric or electrostrictive resonators or networks (H03H3/08 takes precedence)
- H03H 9/02062: {Details relating to the vibration mode}
- H03H 9/19: consisting of quartz
- H03B 2200/0018: relating to the cutting angle of a crystal, e.g. AT cut quartz
- H03H: IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS (waveguides, resonators, lines or other devices of the waveguide type H01P)
- H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H)

## Abstract

A crystal unit includes an AT-cut crystal element that has a planar shape in a rectangular shape and a part as a thick portion. The 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. The first depressed portion is a depressed portion disposed from the thick portion toward the first end portion side, depressed with a predetermined angle θa and subsequently bulged, and connected to the first end portion. The second depressed portion is a depressed portion disposed from the thick portion toward the second end portion side, depressed with a predetermined angle θb and subsequently bulged, and connected to the second end portion.

## Claims

### Claim 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 θa 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 θb 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 λ is a wavelength of a flexure vibration that propagates along an X-axis of a crystal in the crystal unit,
L=λ×(n/2±⅛) (1).

### Claim 2 (depends on 1)

The crystal unit according to claim 1, wherein
the AT-cut crystal element has a long side parallel to the X-axis of the crystal and a short side parallel to a Z′-axis of the crystal, and
the first end portion is positioned on a +X-side.

### Claim 3 (depends on 1)

The crystal unit according to claim 1, wherein:
the AT-cut crystal element has a long side parallel to the X-axis of the crystal and a short side parallel to a Z′-axis of the crystal,
the first end portion is positioned on a +X-side,
the predetermined angle θa is 6°±2°, and
the predetermined angle θb is 16°±2°.