Capacitive sensing apparatus for a vehicle seat

• US 7,217,891 B2
• Filed: 09/29/2005
• Issued: 05/15/2007
• Est. Priority Date: 09/29/2005
• Status: Active Grant

• Current Assignee: Aptiv Technologies AG
• Original Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Inventors: Fischer, Thomas, Fultz, William W., Albani, Mike
• Primary Examiner(s): Gibson; Randy W.
• Application Number:
  US11/239,646
• Publication Number:
  US 20070068720A1
• Time in Patent Office: 593 Days
• Field of Search: 177/144, 177/210.R, 177/210.C, 180/273, 280/735, 738/625.2, 738/626.26, 364/283.1, 364/291
• US Class Current: 177/144
• CPC Class Codes: B60N 2/002 Seats provided with an occupancy detection means mounted therein or thereon detection means responsive to presence or absence of children B60N2/266
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors
• 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 3/13 having piezoelectric or piezoresistive properties
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence

Abstract

A capacitive sensing apparatus for a vehicle seat includes a deflectable dielectric mat and a flexible printed circuit that wraps around the major surfaces of the dielectric mat to define upper and lower conductor strips that overlap in a direction perpendicular to the dielectric mat. Overlapping regions of the conductor strips define an array of capacitive load cells distributed over the seating surface. A connector stub depending from the flexible printed circuit couples the conductor strips to an external circuit that measures the capacitance of the various load cells to determine occupant weight and weight distribution.

Claims

1. Capacitive apparatus for sensing occupant weight applied to a seating surface of a seat, comprising:

a deflectable dielectric mat disposed between said seating surface and a frame of said seat;

an elongate flexible circuit folded around said dielectric mat and supporting first and second sets of conductor strips in proximity to upper and lower surfaces of said dielectric mat, respectively, where said first and second sets of conductor strips periodically overlap in a direction perpendicular to the upper and lower surfaces of said dielectric mat to define a distributed array of capacitive load cells responsive to occupant weight applied to said seating surface; and

capacitance measurement circuitry coupled to said conductor strips for measuring a capacitance of a selected capacitive load cell by coupling a measurement circuit to a pair of conductor strips that define the selected capacitive load cell.

2. The apparatus of claim 1, where the capacitance measurement circuitry applies a reference potential to conductor strips that do not define the selected capacitive load cell.

3. The apparatus of claim 1, where said flexible circuit includes a depending connector stub for coupling said capacitance measurement circuitry to said conductor strips.

4. The apparatus of claim 1, where said capacitance measurement circuitry sequentially measures a capacitance of each capacitive load cell.

5. The apparatus of claim 4, where said capacitance measurement circuitry detects a cumulative change in capacitance of the capacitive load cells as a measure of deformation of said dielectric mat due to occupant weight.

6. The apparatus of claim 4, where said capacitance measurement circuitry detects capacitance changes of said capacitive load cells to determine a distribution of the occupant weight across said seating area.