COMPRESSIBLE CAPACITANCE SENSOR FOR DETERMINING THE PRESENCE OF AN OBJECT

• US 20030005775A1
• Filed: 07/09/2001
• Published: 01/09/2003
• Est. Priority Date: 07/09/2001
• Status: Active Grant

• Current Assignee: Uusi LLC (Nartron Corporation)
• Original Assignee: Nartron Corporation
• Inventors: Perrin, Randall L., Washeleski, John M.
• Granted Patent: US 6,499,359 B1
• Time in Patent Office: Days
• US Class Current: 73/780
• 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: B60N 2/0024 for identifying, categorising or investigation of the occupant or object on the seat
• CPC Class Codes: B60N 2/0025 by using weight measurement
• CPC Class Codes: B60N 2/003 characterised by the sensor mounting location in or on the seat
• CPC Class Codes: B60N 2210/12 Capacitive; Electric field
• CPC Class Codes: B60N 2220/20 using a deterministic algorithm
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: B60R 21/01526 using piezoelectric elements
• CPC Class Codes: B60R 21/01532 using electric or capacitive field sensors
• CPC Class Codes: E05Y 2900/548 Trunk lids
• CPC Class Codes: G01D 5/2417 by varying separation
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

A compressible variable capacitance sensor for determining the presence, size, position, and type of an object such as a human body part includes two flexible conductor elements separated by a non-conductive compressible element. The capacitance of the capacitance sensor changes as a function of force applied by an object on the capacitance sensor. A controller senses the capacitance of the capacitance sensor and controls a device accordingly. The device may be a movable closed opening such as a window in which the controller controls the window as a function of the monitored capacitance to prevent pinching of the object. The device may also be a seat in which the controller determines the characteristics of the seat occupant based on the monitored capacitance.

Claims

1. A sensor for determining the presence of an object, the sensor comprising:

first and second flexible conductor elements separated by a separation distance and having a capacitance dependent on the separation distance; and

a non-conductive compressible element interposed between the first and second flexible conductor elements, wherein the non-conductive compressible element compresses in response to an object applying a force to at least one of the first and second flexible conductor elements such that the separation distance between the first and second flexible conductor elements decreases, wherein the capacitance of the first and second flexible conductor elements changes in response to the separation distance between the first and second flexible conductor elements decreasing.

2. The sensor of claim 1 further comprising:

a controller for monitoring the capacitance of the first and second flexible conductor elements, wherein the controller determines the presence of an object applying a force to at least one of the first and second flexible conductor elements in response to the capacitance of the first and second flexible conductor elements changing.

3. The sensor of claim 1 wherein:

the first flexible conductor element is a center core and the second flexible conductor element coaxially surrounds the non-conductive compressible element and the first flexible conductor element.

4. The sensor of claim 3 wherein:

the second flexible conductor element is electrically grounded.

5. The sensor of claim 3 further comprising:

an elastomeric overcoat coaxially surrounding the second flexible conductor element.

6. The sensor of claim 1 further comprising:

a non-conductive compressible core, wherein the first flexible conductor element coaxially surrounds the non-conductive compressible core, the non-conductive compressible element coaxially surrounds the first flexible conductor element, and the second flexible conductor element coaxially surrounds the non-conductive compressible element.

7. The sensor of claim 1 further comprising:

a third flexible conductor element, wherein the second and third flexible conductor elements are electrically grounded and surround at least a portion of the first flexible conductor element and the non-conductive compressible element is interposed between the first, second, and third flexible conductor elements such that the first and second flexible conductor elements are separated by a first separation distance and have a first capacitance dependent on the first separation distance, and the first and third flexible conductor elements are separated by a second separation distance and have a second capacitance dependent on the second separation distance, wherein the first and second capacitances change in response to the first and second separation distances decreasing when an object applies a force to at least one of the second and third flexible conductor elements.

8. The sensor of claim 1 wherein:

the non-conductive compressible element includes a cell foam.

9. The sensor of claim 1 wherein:

at least one of the first and second flexible conductors elements includes a braided electrically conductive wire.

10. The sensor of claim 1 wherein:

at least one of the first and second flexible conductor elements includes a laminated electrically conductive plate.

11. The sensor of claim 2 wherein:

the controller is operable for generating an offset signal to bias the capacitance between the first and second flexible conductor elements.

12. The sensor of claim 2 wherein:

the controller includes a microprocessor.

13. The sensor of claim 2 wherein:

the controller is operable for executing filtering software to monitor the capacitance between the first and second flexible conductor elements.

14. The sensor of claim 2 wherein:

the controller is operable for executing an adaptive threshold detection algorithm to monitor the capacitance between the first and second flexible conductor elements.

16. The pinch sensor system of claim 15 wherein:

the closed opening device is an electrically operated window.

17. The pinch sensor system of claim 15 wherein:

the closed opening device is an electrically operated door.

18. The pinch sensor system of claim 15 wherein:

the first flexible conductor element is a center core and the second flexible conductor element is electrically grounded and coaxially surrounds the non-conductive compressible element and the first flexible conductor element.

19. The pinch sensor system of claim 18 further comprising:

an elastomeric overcoat coaxially surrounding the second flexible conductor element.

20. The pinch sensor system of claim 15 wherein:

the non-conductive compressible element includes a cell foam.

15. A pinch sensor system for determining the presence of an object within an opening defined by a closed opening device, the pinch sensor system comprising:

a compressible capacitance pinch sensor fixedly positioned adjacent a closed opening device, the compressible capacitance pinch sensor having first and second flexible conductor elements separated by a separation distance, the first and second flexible conductor elements having a capacitance dependent on the separation distance, the compressible capacitance pinch sensor further having a non-conductive compressible element interposed between the first and second flexible conductor elements, wherein the non-conductive compressible element compresses in response to an object within the opening touching the compressible capacitance pinch sensor such that the separation distance between the first and second flexible conductor elements decreases, wherein the capacitance of the first and second flexible conductor elements changes in response to the separation distance between the first and second flexible conductor elements decreasing; and

a controller for monitoring the capacitance of the first and second flexible conductor elements, wherein the controller determines the presence of the object within the opening in response to the capacitance of the first and second flexible conductor elements changing, wherein the controller controls the closed opening device as a function of the change in capacitance.

21. A seat occupant sensor system comprising:

at least one seat occupant sensor disposed within a seat, the at least one seat occupant sensor including first, second, and third flexible conductor plates, wherein the first flexible conductor plate is interposed between the second and third flexible conductor plates such that the first and third flexible conductor plates are separated by a separation distance, wherein the second and third flexible conductor plates are electrically grounded and the first, second, and third flexible conductor plates have a capacitance dependent on the separation distance, the at least one seat occupant sensor further including a first non-conductive compressible element interposed between the first and second flexible conductor plates and a second non-conductive compressible element interposed between the first and third flexible conductor plates, wherein the first and second non-conductive compressible elements compress in response to a seat occupant applying force to the at least one seat occupant sensor such that the separation distance between the second and third flexible conductor plates decreases, wherein the capacitance changes in response to the separation distance decreasing; and

a controller for determining characteristics of the seat occupant as a function of the capacitance of the at least one seat occupant sensor.

22. The seat occupant sensor system of claim 21 wherein:

the at least one seat occupant sensor includes a seat back sensor disposed within a seat back of the seat, wherein the controller determines whether the seat occupant is sitting back on the seat back as a function of the capacitance of the seat back sensor.

23. The seat occupant sensor system of claim 21 wherein:

the at least one seat occupant sensor includes a seat bottom front sensor disposed within a front portion of a seat bottom of the seat, wherein the controller determines whether the seat occupant is sitting short or forward on the seat bottom as a function of the capacitance of the seat bottom front sensor.

24. The seat occupant sensor system of claim 21 wherein:

the at least one seat occupant sensor includes a seat bottom left sensor disposed within a left portion of a seat bottom of the seat and a seat bottom right sensor disposed within a right portion of the seat bottom, wherein the controller determines whether the seat occupant is sitting left or right on the seat bottom as a function of the capacitances of the seat bottom left and right sensors.

25. The seat occupant sensor system of claim 21 wherein:

the at least one seat occupant sensor includes at least one seat bottom sensor disposed within a seat bottom of the seat, wherein the controller determines the weight of the seat occupant as a function of the capacitance of the at least one seat bottom sensor.

26. The seat occupant system of claim 21 wherein:

the controller is operable to reverse the polarity between the first, second, and third flexible conductor plates such that the first conductor plate is electrically grounded, wherein the controller monitors the capacitance of the at least one seat occupant sensor after reversing the polarity to determine whether the seat occupant is an animate or inanimate object.