Capacitive load cell with multi-layer dielectric for extended range

• US 7,176,390 B2
• Filed: 03/02/2005
• Issued: 02/13/2007
• Est. Priority Date: 03/02/2005
• Status: Active Grant

• Current Assignee: Aptiv Technologies AG
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Fultz, William W., Hansen, Mark C.
• Primary Examiner(s): Gibson; Randy W.
• Application Number:
  US11/070,068
• Publication Number:
  US 20060196702A1
• Time in Patent Office: 713 Days
• Field of Search: 738/626.26, 180/273, 280/735, 177/136, 177/144, 177/210.C, 177/225, 361/283.4, 361/291
• US Class Current: 177/136
• CPC Class Codes: G01G 19/4142 for controlling activation of safety devices, e.g. airbag systems electrical circuits for triggering safety arrangements in case of vehicle accidents B60R21/015
• CPC Class Codes: G01G 7/06 by electrostatic action
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence

Abstract

A capacitive load cell includes upper and lower capacitor plates and an intermediate dielectric comprising two or more layers of compressible material with diverse compressibility characteristics. The most easily compressed dielectric layer provides sensitivity to low occupant weight, while the less easily compressed dielectric layer(s) provide sensitivity to medium and high occupant weight.

Claims

1. Capacitive load cell apparatus including first and second conductor plates separated by a compressible dielectric such that force applied to the load cell compresses the dielectric to increase a capacitance between the first and second conductor plates, the improvement wherein:

the compressible dielectric includes at least first and second juxtaposed layers of compressible dielectric material, where the at least first and second layers exhibit different degrees of compressibility such that the capacitance between the first and second conductor plates varies over an extended range of applied force, said first layer becoming fully compressed in response to a first amount of applied force, and said second layer becoming fully compressed in response to a second amount of applied force that is greater than said first amount of applied force.

3. The apparatus of claim 1, where said compressible dielectric exhibits an overall compressibility that is a function of the compressibilities of the at least first and second layers of dielectric material.

4. The apparatus of claim 1, where the at least first and second layers of dielectric material are formed of urethane foam.

2. Capacitive load cell apparatus including first and second conductor plates separated by a compressible dielectric such that force applied to the load cell compresses the dielectric to increase a capacitance between the first and second conductor plates, the improvement wherein:

the compressible dielectric includes first, second and third layers of compressible dielectric material that exhibit successively increasing degrees of compressibility such that the capacitance between the first and second conductor plates varies over an extended range of applied force.