Sensing of seat occupant weight by cushion deformation

• US 20030164715A1
• Filed: 03/04/2002
• Published: 09/04/2003
• Est. Priority Date: 03/04/2002
• Status: Active Grant

• Current Assignee: Temic Automotive of North America, Incorporated (Continental AG)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Lester, Theodore V.
• Granted Patent: US 6,646,452 B2
• Time in Patent Office: Days
• US Class Current: 324/661
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors

Abstract

An apparatus (100) for sensing presence and weight of a vehicle occupant includes a first conductor (120) that is electrically coupled to an oscillating circuit and disposed adjacent a first surface (112) of a compliant pad (110) within the seat of the vehicle. A first conductor (120) generates an oscillating signal at a first intensity. A second conductor (130) is disposed adjacent a second opposing surface (114) of the compliant pad (110) and is capable or receiving the oscillating signal at a second intensity. A detection circuit electrically coupled to the second conductor (130) and capable of receiving the oscillating signal at the second intensity determines the presence and weight of a vehicle occupant based upon the second intensity of the oscillating signal.

Claims

1. An apparatus for sensing the presence and weight of a vehicle occupant, the vehicle including a seat upon which the occupant may sit, the seat including a seat frame, the apparatus comprising:

(a) an oscillating circuit that generates an oscillating signal having a first intensity;

(b) a compliant pad disposed within the seat, the compliant pad located so as to be compressed by an occupant seated upon the seat;

(c) a first conductor, electrically coupled to the oscillating circuit and disposed adjacent a first surface of the compliant pad, the first conductor capable of transmitting the oscillating signal at the first intensity;

(d) a second conductor, disposed adjacent a second surface spaced apart from the first surface of the compliant pad, that is capable of receiving the oscillating signal at a second intensity, the distance between the first conductor and the second conductor varying as the compliant pad is compressed; and

(e) a detection circuit electrically coupled to the second conductor that is capable of receiving the oscillating signal at the second intensity, the second intensity varying in relation to the distance between the first conductor and the second conductor, the detection circuit capable of determining the presence and weight of a vehicle occupant based upon the variation in the second intensity.

2. The apparatus of claim 1, wherein the compliant pad comprises a material having dielectric properties that vary with the compression of the compliant pad, so that the second intensity varies as the compliant pad is compressed in relation to a change in the dielectric properties of the material.

3. The apparatus of claim 1, wherein the compliant pad comprises latex foam.

4. The apparatus of claim 1, wherein the first conductor is bonded to the first surface of the compliant pad.

5. The apparatus of claim 1, wherein the second conductor is bonded to the second surface of the compliant pad.

6. The apparatus of claim 1, wherein the fist conductor is encased within the compliant pad.

7. The apparatus of claim 1, wherein the second conductor is encased within the compliant pad.

8. The apparatus of claim 1, wherein the first conductor comprises a conductive metal foil.

9. The apparatus of claim 1, wherein the second conductor comprises a conductive metal foil.

10. The apparatus of claim 1, wherein the first conductor comprises a conductive coating deposited upon the first surface of the compliant pad.

11. The apparatus of claim 1, wherein the second conductor comprises a conductive coating deposited upon the second surface of the compliant pad.

12. The apparatus of claim 1, wherein the second conductor comprises a plurality of second conductors distributed adjacent the second surface of the compliant pad with a plurality of individual second intensities measured at each conductor location.

13. The apparatus of claim 12, wherein the plurality of individual second intensities measured at the plurality of second conductors are used to characterize an object upon the seat.

14. The apparatus of claim 1, further comprising a guard conductor disposed between the second conductor and the seat frame, wherein each guard conductor shields the second conductor from the seat frame.

15. The apparatus of claim 14, wherein the detection circuit comprises a high impedance amplifier having a first input and a second input, the first input of each amplifier electrically coupled to the second conductor so as to be capable of receiving the oscillating signal at the second intensity, the amplifier capable of generating an amplified signal that has a value that is proportional to the second intensity, the amplified signal being fed back to the second input and being electrically coupled to the guard conductor so as to generate a low impedance source signal sufficient to reduce capacitive loading from the seat frame.

16. A method for sensing the presence and weight of a vehicle occupant, the vehicle including a seat upon which the occupant may sit, the method comprising the steps of:

(a) generating an oscillating signal having a first intensity;

(b) placing a compliant pad within the seat so as to be compressed by an occupant seated upon the seat;

(c) placing a first conductor adjacent to a first surface of the compliant pad, the first conductor being electrically coupled to the oscillating signal and capable of transmitting the oscillating signal at the first intensity;

(d) placing a second conductor adjacent to a second surface spaced apart from the first surface of the compliant pad, the second conductor being capable of receiving the oscillating signal at a second intensity, the distance between the first conductor and the second conductor varying as the compliant pad is compressed; and

(e) receiving the oscillating signal from the second conductor at the second intensity by a detection circuit, the second intensity varying in relation to the distance between the first conductor and the second conductor, the detection circuit determining the presence and weight of a vehicle occupant based upon the variation in the second intensity.

17. The method of claim 16, wherein the compliant pad comprises a material having dielectric properties that vary with the compression of the compliant pad, and wherein the step of receiving the oscillating signal from the second conductor at the second intensity by a detection circuit, the second intensity varying in relation to the distance between the first conductor and the second conductor, the detection circuit determining the presence and weight of a vehicle occupant based upon the variation in the second intensity, is the step of receiving the oscillating signal from the second conductor at the second intensity by a detection circuit, the second intensity varying in relation to the distance between the first conductor and the second conductor and by the change in the dielectric properties of the material as the compliant pad is compressed, the detection circuit determining the presence and weight of a vehicle occupant based upon the variation in the second intensity.