ACCELERATION SENSOR

• US 20140091404A1
• Filed: 10/02/2013
• Published: 04/03/2014
• Est. Priority Date: 10/02/2012
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Yamaha Corporation
• Inventors: SUZUKI, TOSHIHISA
• Granted Patent: US 9,315,377 B2
• Time in Patent Office: Days
• US Class Current: 257/415
• CPC Class Codes: B81B 3/0018 Structures acting upon the moving or flexible element for transforming energy into mechanical movement or vice versa, i.e. actuators, sensors, generators
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• 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

Abstract

A first sensor section installed in an acceleration sensor employs a first elastic member which is elastically movable according to acceleration in the first and third directions and is stiff against acceleration in second direction so as to restrict elasticity in second direction. Thereby, the first sensor section is provided as a biaxial acceleration sensor which detects the first and third directional acceleration according to a change of electrostatic capacity between a first weight (i.e. the first movable electrode) made movable according to acceleration and the first fixed electrode. A second sensor section installed in the acceleration sensor is structurally identical with the first sensor section and configured to detect acceleration in second and third directions. Thereby, such combination of the first sensor section and the second sensor section constitutes a three-dimensional acceleration sensor.

Claims

1. An acceleration sensor comprising:

a substrate;

a first elastic member that is fixed to the substrate at one end thereof and configured to move elastically according to acceleration with respect to two different directions one of which is a first direction parallel to a plane of the substrate and other one of which is a third direction perpendicular to the plane of the substrate;

a second elastic member that is fixed to the substrate at one end thereof and configured to move elastically according to acceleration with respect to two different directions one of which is a second direction being perpendicular to the first direction and parallel to the plane of the substrate, and other one of which is the third direction;

a first weight which is connected to the other end of the first elastic member and movably supported apart from the substrate;

a second weight which is connected to the other end of the second elastic member and movably supported apart from the substrate; and

a set of three sensor sections comprising a first sensor section, a second sensor section and a third sensor section which respectively detect acceleration in the first direction, acceleration in the second direction and acceleration in the third direction according to movement of the first weight and the second weight.

2. The acceleration sensor according to claim 1,

wherein the first sensor section comprises:

a first fixed electrode that is formed into a plane in parallel to the second direction and the third direction, and arranged on the substrate; and

a first movable electrode that is formed into a plane in parallel to the second direction and the third direction, and arranged on the first weight,

wherein the first fixed electrode and the first movable electrode make up a first electrostatic capacitor which detects acceleration in the first direction according to movement of the first weight in the first direction,

wherein the second sensor section comprises;

a second fixed electrode that is formed into a plane in parallel to the first direction and the third direction, and arranged on the substrate; and

a second movable electrode that is formed into a plane in parallel to the first direction and the third direction, and arranged on the first weight,

wherein the second fixed electrode and the second movable electrode make up a second electrostatic capacitor which detects acceleration in the second direction according to movement of the second weight in the second direction; and

wherein the third sensor section comprises;

a third fixed electrode that is formed into a plane in parallel to the substrate, and arranged on the substrate; and

a third movable electrode that is formed into a plane in parallel to the substrate, and arranged on at least one of the first weight and the second weight,

wherein the third fixed electrode and the third movable electrode make up a third electrostatic capacitor which detects acceleration in the third direction according to movement of at least one of the first weight and the second weight in the third direction.

3. The acceleration sensor according to claim 2,

wherein there are provided two of the third movable electrode arranged on the first weight and the second weight in the third sensor section, and

wherein the acceleration in the third direction is detected by summing up capacities of two of the third electrostatic capacitors made up by the third fixed electrode and the two of the third movable electrodes.

4. The acceleration sensor according to claim 1,

wherein the first elastic member is configured such that a spring constant in the second direction is larger than spring constants in the first and third directions, and

wherein the second elastic member is configured such that a spring constant in the first direction is larger than spring constants in the second and third directions.

5. The acceleration sensor according to claim 2,

wherein a capacity of the third electrostatic capacitor of the third sensor section is larger than capacity of the first electrostatic capacitor of the first sensor section and capacity of the second electrostatic capacitor of the second sensor section.

6. The acceleration sensor according to claim 1,

wherein a sensitivity of detecting acceleration in the first direction by the first sensor section, a sensitivity of detecting acceleration in the second direction by the second sensor section and a sensitivity of detecting acceleration in the third direction by the third sensor section are substantially equal.

7. The acceleration sensor according to claim 1,

wherein the first elastic member and the second elastic member are structurally identical and the first sensor section and the second sensor section are structurally identical.

8. The acceleration sensor according to claim 1,

wherein the first elastic member includes a first spring structure with such configuration that a side stretching in the first direction and a side stretching in the second direction alternately connect and continue in the second direction in a zigzag manner and end-to-end length of the first elastic member is longer than the side stretching in the first direction, and

wherein the second elastic member includes a second spring structure with such configuration that a side stretching in the first direction and a side stretching in the second direction alternately connect and continue in the first direction in a zigzag manner and end-to-end length of the second elastic member is longer than the side stretching in the second direction.