Method and apparatus for detecting the occupancy of a vehicle seat

• US 3,912,939 A
• Filed: 04/01/1974
• Issued: 10/14/1975
• Est. Priority Date: 04/01/1974
• Status: Expired due to Term

• Current Assignee: Chen Y.I. Lee, Norman G. Quantz
• Original Assignee: Chen Y.I. Lee, Norman G. Quantz
• Inventors: Quantz, Norman G., Lee, Chen Yi
• Primary Examiner(s): Hohauser, Herman
• Application Number:
  US05/456,679
• Time in Patent Office: 561 Days
• Field of Search: 180/82C 340/52E,258C,278 317/DIG.2 307/1SB 280/15SB
• US Class Current: 340/573.1
• CPC Class Codes: B60R 2022/4816 for sensing locking of buckle
• CPC Class Codes: B60R 2022/4858 for sensing pressure on seat
• CPC Class Codes: B60R 2022/4866 Displaying or indicating arrangements thereof
• CPC Class Codes: B60R 2022/4891 preventing use of the vehicle when the seatbelt is not fastened
• CPC Class Codes: B60R 22/48 Control systems, alarms, or interlock systems, for the correct application of the belt or harness

Abstract

A seat occupant seat detector for a safety belt interlock/warning system including a square wave generator, a reference capacitor which is connected to receive the square wave, a large area conductor positioned in the seat bottom which is connected to receive the square wave, and a logic circuit responsive to the relative capacitance of the reference capacitor and the seat conductor comprising a pair of NAND gates connected to the capacitor and the seat conductor and arranged to provide an output signal in response to the relative rise time of the square wave at the capacitor and at the seat conductor.

Claims

1. An apparatus for detecting the occupancy of a seat or the like by an occupant comprising:

generating means for providing a time varying signal;

reference capacitor means having a reference value of capacitance and operatively connected to said generating means to receive said signal;

conductor means also operatively connected to said generating means to receive said signal and mountable in association with said seat so as to be in a position in the vicinity of said occupant, said conductor means being adapted to have a first value of capacitance when said seat is unoccupied and a second value of capacitance when said occupant occupies said seat; and

detecting means operatively connected with said reference capacitor and said conductor means for detecting the change of the value of capacitance of said conductor means from said first value of capacitance to said second value of capacitance by responding to the relative capacitance of said reference capacitor means and said conductor means to provide a signal representative of said occupancy.

2. An apparatus according to claim 1 wherein said generating means provides a time varying signal having a predetermined wave shape which is altered by the value of capacitance of said reference capacitor means to provide a reference altered signal and is altered by the value of capacitance of said conductor means to provide an occupant altered signal and wherein said detecting means receives said reference altered signal and said occupant altered signal and detects the relative capacitance of said reference capacitor means and said conductor means by responding to the shape of the reference and occupant altered signals.

3. An apparatus according to claim 1 wherein said generating means is an oscillator which provides a repetitive signal.

4. An apparatus according to claim 1 wherein said generating means provides a square wave.

5. An apparatus according to claim 2 wherein said detecting means compares the rise or decay of said reference and occupant altered signals.

6. An apparatus according to claim 5 wherein said detecting means compares the rate of rise or decay of said reference and occupant altered signals.

7. An apparatus according to claim 5 wHerein said detecting means includes threshold means for receiving said reference and occupant altered signals for responding to the time at which said reference and occupant altered signals attain a predetermined threshold value.

8. An apparatus according to claim 7 wherein said threshold means includes a logic circuit which responds to the attainment of said threshold by providing an output signal which changes from a first condition to a second condition upon the attainment of said threshold.

9. An apparatus according to claim 7 wherein said threshold means includes a pair of threshold devices with one of said threshold devices receiving said reference altered signal and the other of said threshold devices receiving said occupant altered signal for determining which of the reference and occupant altered signals first attains a predetermined threshold value.

10. An apparatus according to claim 9 wherein said detecting means includes means for inhibiting one of said pair of threshold devices when the altered signal received by the other of said pair of threshold devices first attains said predetermined threshold value.

11. An apparatus according to claim 10 wherein each of said pair of threshold devices has an output terminal for providing a predetermined output signal upon attainment of said threshold value by its respective one of said altered signals, the output terminal of one of said threshold devices being connected to the other threshold device to inhibit said other threshold device from providing its predetermined output signal when the one threshold device has provided its predetermined output signal.

12. An apparatus according to claim 11 wherein each of said threshold devices is a logic circuit having said output terminal for providing an output signal having two logic states with one of said logic states representing said predetermined output signal.

13. An apparatus according to claim 12 wherein said logic device is a NAND gate.

14. An apparatus for detecting the occupancy of a seat or the like by an occupant comprising:

oscillator means for providing a repetitive time varying signal having a predetermined wave shape;

reference capacitor means receiving said signal for altering the wave shape of said signal in accordance with the value of capacitance of said reference capacitor means to provide a reference altered signal;

conductor means receiving said signal which is mountable in association with said seat so as to be in a position in the vicinity of said occupant when said occupant occupies said seat so that the value of capacitance of said conductor will be changed by said occupancy, said conductor means altering the wave shape of said signal in accordance with the value of capacitance of said conductor for providing an occupant altered signal; and

comparator means receiving said reference altered signal and said occupant altered signal for determining a change in the wave shape of said occupant altered signal relative to said reference altered signal upon the change in capacitance of said conductor means when said occupant occupies said seat to provide a signal representative of said occupancy.

15. An apparatus according to claim 14 wherein said oscillating means provides a square wave.

16. An apparatus according to claim 14 wherein said comparator means compares the rise or decay of said reference and occupant altered signals.

17. An apparatus according to claim 16 wherein said comparator means compares the rate of rise or decay of said reference and occupant altered signals.

18. An apparatus according to claim 17 wherein said comparator means compares the rate of rise of said reference and occupant altered signals.

19. An apparatus according to claim 16 wherein said comparator means includes a threshold means for receiving said reference and occupant altered signals for responding to the time at which said reference and occupant altered signals attain a predetermined threshold value.

20. An apparatus according to claim 19 wherein said comparator means includes a logic circuit which responds to the attainment of said threshold by providing an output signal which changes from a first condition to a second condition upon the attainment of said threshold.

21. An apparatus according to claim 20 wherein said threshold means includes a pair of threshold devices with one of said threshold devices receiving said reference altered signal and the other of said threshold devices receiving said occupant altered signal for determining which of the reference and occupant altered signals first attains a predetermined threshold value.

22. An apparatus according to claim 21 wherein said comparator means includes means for inhibiting one of said pair of threshold devices when said altered signals received by the other of said pair of threshold devices first attains said predetermined threshold value.

23. An apparatus according to claim 22 wherein each of said pair of threshold devices has an output terminal for providing a predetermined output signal upon attainment of said threshold value by its respective one of said altered signals, the output terminal of one of said threshold devices being connected to the other threshold device to inhibit said other threshold device from providing its predetermined output signal when the one threshold device has provided its predetermined output signal.

24. An apparatus according to claim 23 wherein each of said threshold devices is a logic circuit having said output terminal for providing an output signal having two logic states with one of said logic states representing said predetermined output signal.

25. An apparatus according to claim 24 wherein said logic device is a NAND gate.

26. An apparatus according to claim 14 wherein said reference capacitor means has a value of capacitive which is intermediate the value of capacitance of said conductor means before said occupancy and the value of capacitance of said conductor means after said occupancy.

27. A method for detecting the occupancy of a seat or the like by an occupant comprising the steps of:

supplying a time varying signal to a reference capacitor;

supplying a time varying signal to a conductor associated with the seat and positioned to be in the vicinity of said occupant when said occupant occupies said seat so that the value of capacitance of said conductor will be affected by said occupancy; and

comparing the value of capacitance of said reference capacitor with the value of capacitance of said conductor before and after said occupant occupies said seat to detect the change in the value of capacitance of said conductor relative to said reference capacitor when said occupant occupies said seat.