ACCELERATION SENSOR

• US 20140144235A1
• Filed: 11/26/2013
• Published: 05/29/2014
• Est. Priority Date: 11/27/2012
• Status: Active Grant

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Yamaha Corporation
• Inventors: Suzuki, Toshihisa
• Granted Patent: US 9,316,666 B2
• Time in Patent Office: Days
• US Class Current: 73/514.32
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• 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 2015/0814 for translational movement of the mass, e.g. shuttle type
• CPC Class Codes: G01P 2015/0871 using stopper structures for limiting the travel of the seismic mass

Abstract

An acceleration sensor achieving improvement of sensitivity and comprehensive miniaturization as a device includes a first sensor. The first sensor is furnished with an electrostatic capacitor that is configured such that a first fixed electrode, a second fixed electrode and a movable electrode are intensively arranged in a row. In the electrostatic capacitor, the first fixed electrode, the second fixed electrode and the movable electrode are arranged adjoining one another in acceleration detection direction (y-axis direction) at a position corresponding to the center of a weight in a plane view of a substrate. At one of longitudinal-side'"'"'s ends of each electrode (one of ends in x-axis direction), connectors are provided so as to connect the first fixed electrode and the second fixed electrode to the substrate by connectors.

Claims

1. An acceleration sensor comprising:

a substrate;

a weight that is movably arranged apart from the substrate; and

an electrostatic capacitor, equipped with fixed electrodes and movable electrodes, of which electrostatic capacity varies according to distance between each of the fixed electrodes and each of the movable electrodes in a detection direction, the distance varying according to an acceleration working in the detection direction that is parallel to a flat surface direction of the substrate,

wherein, the electrostatic capacitor is arranged at center of a region surrounded by a periphery of the weight in a plane view of the substrate, so that each of the fixed electrodes and each of the movable electrodes are arranged alternately in a row along the detection direction.

2. The acceleration sensor according to claim 1,

wherein center of the electrostatic capacitor is arranged at the center of the region surrounded by the periphery of the weight in the plane view of the substrate.

3. The acceleration sensor according to claim 1,

wherein the center of the region surrounded by the periphery of the weight is center of gravity of the weight.

4. The acceleration sensor according to claim 1,

wherein a set of the fixed electrodes includes:

a first fixed electrode and a second fixed electrode arranged so as to adjoin each other within a region between neighboring two of the movable electrodes;

a first connector that connects the first fixed electrode and the substrate; and

a second connector that connects the second fixed electrode and the substrate,

wherein the first connector is configured to be wide toward the second fixed electrode adjoining the first fixed electrode so that the first fixed electrode faces the movable electrode in a state of a straight line, and

wherein the second connector is configured to be wide toward the first fixed electrode adjoining the second fixed electrode so that the second fixed electrode faces the movable electrode in a state of a straight line.

5. The acceleration sensor according to claim 1,

wherein each of the fixed electrodes is fixed to the substrate and formed in a plate of which surface is perpendicular to both the flat surface direction of the substrate and the detection direction, and

wherein each of the movable electrodes is configured to extend from the weight and formed in a plate of which surface faces each of the fixed electrodes in parallel.

6. The acceleration sensor according to claim 1,

wherein each of the fixed electrodes includes a set of a first fixed electrode and a second fixed electrode arranged so as to adjoin each other within a region between neighboring two of the movable electrodes, and

wherein, when the weight moves, a capacity change subject to the first fixed electrode and the movable electrode adjoining the first fixed electrode and a capacity change subject to the second fixed electrode and the movable electrode adjoining the second fixed electrode are made in an inverse direction for each other.

7. The acceleration sensor according to claim 1,

wherein each of the movable electrodes is configured to extend from the weight and equipped with at least two fixed portions to be connected to the weight.

8. The acceleration sensor according to claim 7,

wherein the fixed portions are provided at both ends of each of the movable electrodes.

9. The acceleration sensor according to 8,

wherein each of the movable electrodes is formed in a plate of which surface is perpendicular to both the flat surface direction of the substrate and the detection direction, and

wherein the fixed portions are provided at both ends of the plate of each of the movable electrodes.

10. The acceleration sensor according to claim 1 further comprising:

restrictors that restrict a movement of the weight in the detection direction when the acceleration works and causes the weight to move in the detection direction,

wherein, when there is defined a rectangular frame surrounding the fixed electrodes as a whole in the plane view of the substrate and consisting of four sides two of which being parallel with the detection direction and other two of which being perpendicular to the detection direction, with reference to four apexes of the rectangular frame, the substrate is divided into nine regions by two first lines each passing through two of apexes positioned in a direction perpendicular to the detection direction and two second lines each passing through two of apexes positioned in the detection direction, and

wherein the restrictors restrict movement of the weight at each of four regions occupying four corners of the substrate divided into nine regions, the four regions being regions other than a region containing the fixed electrodes and regions adjoining the region containing the fixed electrodes.

11. The acceleration sensor according to claim 10,

wherein each of the fixed electrodes is formed in a plate of which surface is perpendicular to both the flat surface direction of the substrate and the detection direction, and the fixed electrodes are arranged in the detection direction, and

wherein the rectangular frame is set so as to surround periphery of the fixed electrodes as a whole.

12. The acceleration sensor according to claim 10,

wherein the restrictors are fixed to the substrate at the four regions so that the restrictors are symmetrically positioned with reference to center of gravity of the weight.