Capacitive acceleration sensor

• US 5,900,550 A
• Filed: 06/16/1997
• Issued: 05/04/1999
• Est. Priority Date: 06/16/1997
• Status: Expired due to Term

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Ford Motor Company
• Inventors: Menzel, Christoph P.
• Primary Examiner(s): Brock, Michael
• Assistant Examiner(s): Kwok, Helen C.
• Application Number:
  US08/876,575
• Time in Patent Office: 687 Days
• Field of Search: 73/514.32, 73/514.36, 73/514.29, 73/514.21, 73/514.16, 361/280, 361/283.1
• US Class Current: 73/514.32
• 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

An accelerometer includes an axis about which opposing sides having different mass and different capacitor plates sizes move in response to acceleration. The different size of capacitor plate improves linearity of the capacitor sensing structure.

Claims

1. An accelerometer, including:

a substrate;

a sensing element having a metallic member;

mounting means positioned between said sensing element and said substrate so that the sensing element is positioned adjacent the substrate, whereby acceleration normal to the substrate tends to move the sensing element;

means for sensing movement of the sensing element including a first metallic electrode mounted on the substrate below the sensing element and a second, electrically independent metallic electrode also mounted below the sensing element wherein the size of the first and second metallic electrodes are unequal;

said sensing element includes an internal opening;

said mounting means are positioned within said opening for mounting the sensing element so that the sensing element is positioned above the substrate and can rotate about a torsional axis that is above and substantially parallel to the substrate, the mounting means comprising a pedestal mounted to the substrate and flexible support means for providing a connection between the sensing element and the pedestal, the support means comprising a beam extending between the sensing element and pedestal in a direction parallel to the sensing element and substrate and perpendicular to the torsional axis, the torsional axis dividing the sensing element into a first section on one side of the torsional axis and a second section on the opposite side of the torsional axis from the first section, the total moments of the first and second sections about the torsional axis being different from one another, whereby acceleration normal to the substrate tends to rotate the sensing element about the torsional axis; and

means for sensing rotation of the sensing element about the torsional axis including a first capacitor formed by the first section of the element and the first metallic electrode mounted on the substrate, below the first section of the element and a second capacitor on the opposite side of the torsional axis from the first capacitor, formed by the second section of the element and the second metallic electrode mounted on the substrate below the second section of the element wherein the size of the first and second capacitors is unequal.

2. An accelerometer as recited in claim 1 further comprising an electronic module for processing signals received from said first and second capacitors.