Angular velocity sensor and manufacturing method therefor

Patent metadata

Field	Value
Publication number	US-9702698-B2
Application number	US-201514809941-A
Country	US
Kind code	B2
Filing date	Jul 27, 2015
Priority date	Feb 4, 2013
Publication date	Jul 11, 2017
Grant date	Jul 11, 2017

Abstract

One or more vibration plate layers of a diaphragm part are formed by a thin film forming technique. When a resonance frequency in a resonance vibration mode calculated from dimensions of a structure of an angular velocity sensor and an elastic parameter of a material thereof is defined as f kilohertz, a mass of a weight part is defined as M milligrams, a circumference of the diaphragm part is defined as r meters, a stress applied to a piezoelectric layer is defined as σ p pascals, a thickness thereof is defined as t p meters, a stress applied to an n-th layer from the weight part in a vibration plate portion constituted by a plurality of layers including a lower electrode and the vibration plate layers is defined as σ n pascals, and a thickness thereof is defined as t n meters (where n is a natural number), T eff expressed by T eff =r(σ p t p +Σσ n t n )/M satisfies {(−0.36f 2 +210)/33}≦T eff ≦{(0.44f 2 +210)/33}.

First claim

What is claimed is:

1. An angular velocity sensor comprising:
a flexible diaphragm part including a laminated structure, the laminated structure of the diaphragm part including an upper electrode, a piezoelectric layer, a lower electrode, and one or more vibration plate layers, the upper electrode including a driving electrode part and a detection electrode part, the driving electrode part and the detection electrode part being pattern-arranged;
a pedestal section configured to support an outer circumference of the diaphragm part; and
a weight section joined to a central part of the diaphragm part,
the angular velocity sensor being configured to cause the weight section to vibrate using an inverse piezoelectric effect of a piezoelectric body by applying an electric field to the piezoelectric layer via the driving electrode part, and detect a displacement generated in the weight section based on a Coriolis force, the displacement being detected by a piezoelectric effect from the detection electrode part,
the vibration plate layer being formed by a thin film forming technique, and
when a resonance frequency in a resonance vibration mode calculated from dimensions of a structural body of the angular velocity sensor and an elastic parameter of a material of the structural body is f kilohertz, a mass of the weight section is M milligrams, a circumferential length of the diaphragm part is r meters, a stress acting on the piezoelectric layer is σ P pascals, a film thickness of the piezoelectric layer is t P meters, a stress acting on an n-th layer of a vibration plate portion constituted by a plurality of layers including the lower electrode and the one or more vibration plate layers is σ n pascals, the n-th layer being n-th from a side of the weight section, and a film thickness of the n-th layer being t n meters, and when n is a natural number, then, an effective tension, T eff that is expressed by an expression:

T
eff

=

r
(

σ
p

⁢

t
p

+

∑
n

⁢

σ
n

⁢

t
n

)

M

satisfies:

-
0.36

⁢

f
2

+
210

33

≤

T
eff

≤

0.44
⁢

f
2

+
210

33

.

2. The angular velocity sensor as set forth in claim 1 ,
wherein a following expression is satisfied:

-
0.28

⁢

f
2

+
210

33

≤

T
eff

≤

0.32
⁢

f
2

+
210

33

.

3. The angular velocity sensor as set forth in claim 1 ,
wherein a following expression is satisfied:

-
0.19

⁢

f
2

+
210

33

≤

T
eff

≤

0.21
⁢

f
2

+
210

33

Assignees

• Fujifilm Corp

Inventors

• Naono Takayuki
• Nakano Takuma

Classifications

• G01C19/5712 Primary

  the devices involving a micromechanical structure · CPC title

• G01C19/56 Primary

  Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces · CPC title

• G01C25/00 Primary

  Manufacturing, calibrating, cleaning, or repairing instruments or devices referred to in the other groups of this subclass (testing, calibrating or compensating compasses G01C17/38) · CPC title

• G01P15/09

  by piezoelectric pick-up · CPC title

• G01P15/097

  by vibratory elements · CPC title