Bending beam accelerometer with differential capacitive pickoff

• US 20040187578A1
• Filed: 03/26/2003
• Published: 09/30/2004
• Est. Priority Date: 03/26/2003
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Horning, Robert D., Becka, Stephen F., Malametz, David L.
• Granted Patent: US 6,912,902 B2
• Time in Patent Office: Days
• US Class Current: 73/514.36
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 3/0072 For controlling internal stress or strain in moving or flexible elements, e.g. stress compensating layers
• CPC Class Codes: G01P 15/08 with conversion into electric or magnetic values
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• 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

A low cost, pendulous, capacitive-sensing Micro Electro-Mechanical Systems (MEMS) accelerometer is provided. The accelerometer includes a pendulous proof mass, one or more securing pads, and one or more flexures coupled with the pendulous proof mass and the one or more securing pads. The flexures flex linearly with respect to motion of the pendulous proof mass. First and second capacitor plates are positioned relative to the pendulous proof mass for detecting motion of the proof mass according to a sensed difference in capacitance. One or more strain isolation beams are connected between the one or more flexures and the pendulous proof mass or the securing pads. The strain isolation beams protect the flexures from mechanical strain.

Claims

1. A micro electro-mechanical systems accelerometer, the accelerometer comprising:

a pendulous proof mass;

one or more securing pads; and

one or more flexure beams coupled with the pendulous proof mass and the one or more securing pads, wherein the flexure beams have approximately the same thickness as the proof mass and have a longitudinal axis that is oriented approximately orthogonal to an axis of rotation of the proof mass; and

one or more first strain isolation beams connected between the one or more flexure beams and the pendulous proof mass.

2. The accelerometer of claim 1, further comprising one or more second strain isolation beams connected between the one or more flexure beams and the securing pads.

3. The accelerometer of claim 2, wherein the one or more first strain isolation beams includes a slot for limiting travel of the pendulous proof mass to less than failure strain of the accelerometer.

4. The accelerometer of claim 1, wherein the securing pads are separated from the pendulous proof mass based on a failure strain value of the accelerometer.

5. The accelerometer of claim 1, further comprising first and second capacitor plates, wherein the first capacitor plate is positioned relative to a first section of the pendulous proof mass, and the second capacitor plate is positioned relative to a second section of the pendulous proof mass.

6. A micro electro-mechanical systems accelerometer, the accelerometer comprising:

a pendulous proof mass;

one or more securing pads;

one or more flexure beams coupled with the pendulous proof mass and the one or more securing pads, wherein the flexure beams have approximately the same thickness as the proof mass and have a longitudinal axis that is oriented approximately orthogonal to an axis of rotation of the proof mass; and

one or more strain isolation beams connected between the flexure beams and the pendulous proof mass and the securing pads,

wherein the strain isolation beams protect the flexures from mechanical shock, and the securing pads are separated from the pendulous proof mass for protecting the flexures from mechanical shock.

7. The accelerometer of claim 6, further comprising slots for limiting travel of the pendulous proof mass to less than failure strain of the accelerometer and the separation of the securing pads from the pendulous proof mass limits travel of the pendulous proof mass to less than failure strain of the accelerometer.