ACCELERATION SENSOR

• US 20110138914A1
• Filed: 11/19/2009
• Published: 06/16/2011
• Est. Priority Date: 11/25/2008
• Status: Active Grant

• Current Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Electric Works Company Limited (Panasonic Holdings Corporation)
• Inventors: Suzuki, Yuji, Okada, Takeshi, Yoshida, Hitoshi, Ueda, Hideki, Ibara, Nobuyuki
• Granted Patent: US 8,850,889 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 2015/0831 the mass being of the paddle type having the pivot axis between the longitudinal ends of the mass, e.g. see-saw configuration

Abstract

An acceleration sensor includes: a rectangular moving electrode; a pair of beams which connect to centers of two opposite sides of the moving electrode, and support the moving electrode freely swingably; and first and second fixed electrodes which are provided on one side and other side of a boundary line, respectively, and are arranged to be opposed to a front surface of the moving electrode at a predetermined interval. A straight line that connects the pair of beams to each other is taken as the boundary line. Then, on a back surface of the moving electrode, first and second recessed portions are formed on one side of the boundary line and the other side thereof, respectively.

Claims

1. An acceleration sensor comprising:

a rectangular moving electrode;

a pair of beams which connect to centers of two opposite sides of the moving electrode, and support the moving electrode freely swingably; and

first and second fixed electrodes which are provided on one side and other side of a boundary line, respectively, and are arranged to be opposed to a front surface of the moving electrode at a predetermined interval, wherein a straight line that connects the pair of beams to each other is taken as the boundary line,

wherein, on a back surface of the moving electrode, first and second recessed portions are formed on one side of the boundary line and the other side thereof, respectively.

2. The acceleration sensor according to claim 1, wherein the acceleration sensor detects acceleration in a first direction, which is applied to the moving electrode, and acceleration in a second direction, which is applied to the moving electrode and is orthogonal to the acceleration in the first direction.

3. The acceleration sensor according to claim 1, further comprising:

a frame that incorporates the moving electrode therein; and

first and second detecting electrodes formed in the frame and electrically connected to the first and second fixed electrodes, respectively,

wherein gaps are formed between the first detecting electrode and the second detecting electrode, between the first and second detecting electrodes and the frame, and between the first and second detecting electrodes and the moving electrode.

4. The acceleration sensor according to claim 1, further comprising:

protrusions formed on opposite surfaces of the first and second fixed electrodes to the moving electrode or on an opposite surface of the moving electrode to the first and second fixed electrodes.

5. The acceleration sensor according to claim 4, wherein the protrusions are formed of silicon, silicon oxide or a carbon material.

6. The acceleration sensor according to claim 1, further comprising:

a fixed plate arranged to be opposed to the back surface of the moving electrode at a predetermined interval,

wherein an adhesion prevention film, which prevents adhesion between the moving electrode and the fixed plate, is formed on a surface of the fixed plate, and the surface is opposed to the moving electrode.

7. The acceleration sensor according to claim 6, wherein the adhesion prevention film is formed of a same material as that of the first and second fixed plates.

8. The acceleration sensor according to claim 6, wherein an organic material thin film is formed on a front surface of the adhesion prevention film.

9. The acceleration sensor according to claim 1, wherein an angle made by a perpendicular line drawn down from a center of gravity of the moving electrode to the front surface thereof and a straight line that connects the center of gravity of the moving electrode and the boundary line to each other is approximately 45 degrees.

10. The acceleration sensor according to claim 1, wherein a metal material is embedded in the second recessed portion.

11. The acceleration sensor according to claim 10, wherein the metal material is formed of a metal material having specific gravity equal to or larger than specific gravity of a material for forming the moving electrode.

12. The acceleration sensor according to claim 10, wherein weight of the metal material is substantially equal to weight of a reinforcement member that constructs an outer wall of the first recessed portion.

13. An acceleration sensor structure comprising:

a plurality of the acceleration sensors, each acceleration sensor according to claim 1,

wherein the acceleration sensors are formed in a same chip plane.

14. The acceleration sensor structure according to claim 13, wherein two of the acceleration sensors are arranged in the same chip plane, and

one of the acceleration sensors is arranged to rotate by 180 degrees with respect to the other acceleration sensor in the chip plane.

15. The acceleration sensor structure according to claim 13, wherein three of the acceleration sensors are arranged in the same chip plane, and

second and third acceleration sensors are arranged to rotate by 90 degrees and 180 degrees, respectively with respect to a first acceleration sensor in the chip plane.