CRYSTAL UNIT

• US 20190326876A1
• Filed: 04/23/2019
• Published: 10/24/2019
• Est. Priority Date: 04/24/2018
• Status: Active Grant

• Current Assignee: Nihon Dempa Kogyo Company Limited
• Original Assignee: Nihon Dempa Kogyo Company Limited
• Inventors: TOSHIKAWA, Koji, YOSHIDA, Shinobu, IWATA, Hirokazu
• Granted Patent: US 10,771,038 B2
• Time in Patent Office: Days
• CPC Class Codes: H03B 2200/0018 relating to the cutting angle of a crystal, e.g. AT cut quartz
• CPC Class Codes: H03B 5/32 being a piezoelectric resonator selection of piezoelectric material H10N30/00
• CPC Class Codes: H03H 3/02 for the manufacture of piezoelectric or electrostrictive resonators or networks H03H3/08 takes precedence
• CPC Class Codes: H03H 9/02023 consisting of quartz
• CPC Class Codes: H03H 9/02062 Details relating to the vibration mode
• CPC Class Codes: H03H 9/19 consisting of quartz

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

1. A crystal unit, comprising:

an AT-cut crystal element that has a planar shape in a rectangular shape 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 θ

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 θ

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 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).

2. 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.

3. 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 θ

a is 6°

±

2°

, and

the predetermined angle θ

b is 16°

±

2°

.