Seat Belt Tension Sensor

• US 20030150283A1
• Filed: 02/12/2003
• Published: 08/14/2003
• Est. Priority Date: 02/13/2002
• Status: Active Grant

• Current Assignee: TK Holdings Incorporated (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Automotive Systems Laboratory, Incorporated (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Wilson, David S., Steele, Ryan N., McDonnell, Judson G., Duda, Donald A., Stanley, James G.
• Granted Patent: US 6,829,952 B2
• Time in Patent Office: Days
• US Class Current: 73/862.391
• CPC Class Codes: G01L 5/103 using sensors fixed at one end of the flexible member

Abstract

An anchor plate operatively coupled to a seat belt incorporates a slot that slideably engages an anchor bolt, which is biased therein by a spring. A tension in the seat belt causes a deflection of the spring and an associated motion of the anchor bolt in the slot, which is sensed by a proximity sensor on the anchor plate. In another aspect, a carriage is adapted to slide relative to a bracket, and a first spring is operative between the carriage and the bracket so as to bias the carriage relative to the bracket in a direction opposite to a first direction. Either the bracket is operatively coupled to a vehicle frame with an anchor bolt and the seat belt operatively engages the carriage, or vice versa. A tension in the seat belt, when reacted by the anchor bolt, causes an associated motion of the carriage in the first direction, which is sensed by a displacement sensor. In one embodiment, a second spring is operative between the carriage and the bracket so as to bias the carriage in the first direction relative to said bracket, thereby substantially eliminating slack. One embodiment of the displacement sensor comprises a magnetic sensor coupled to the bracket, which measures the magnetic field between a pair of magnets having crossed pole orientations, operatively coupled to the carriage. In another aspect, a second carriage and associated displacement sensor provide an additional measure of tension.

Claims

1. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt, comprising:

a. an anchor plate, wherein said anchor plate is adapted to operatively couple to a webbing of a seat belt;

b. a first slot in said anchor plate, wherein said first slot is adapted to provide for operatively coupling said anchor plate to the vehicle frame with the anchor bolt through said first slot, said first slot slideably engages the anchor bolt, and said first slot is adapted to limit the travel of the anchor bolt relative to said first slot responsive to a tension applied to the seat belt when the seat belt is operatively coupled to said anchor plate and said anchor plate is operatively coupled to the vehicle frame with the anchor bolt through said first slot;

c. a spring operative between said anchor plate and the anchor bolt when said anchor plate is operatively coupled to the vehicle frame with the anchor bolt, wherein said spring biases said slot relative to the anchor bolt, a tension in the seat belt causes a deflection of said spring and an associated motion of the anchor bolt in said slot, and the magnitude of said deflection is responsive to a magnitude of said tension; and

d. at least one proximity sensor operatively coupled to said anchor plate, wherein said at least one proximity sensor is responsive to a proximity thereof to the anchor bolt, and thereby, said proximity sensor is responsive to a position of the anchor bolt within said first slot responsive to deflection of said spring responsive to said tension in the seat belt.

2. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 1, wherein said anchor plate comprises an attachment opening, and said anchor plate is operatively coupled to said webbing by looping said webbing through said attachment opening.

3. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 1, wherein said spring comprises a tension spring operatively coupled to said anchor plate at a location between the anchor bolt and a location where said anchor plate is operatively coupled to the webbing of the seat belt.

4. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 1, wherein at least one said proximity sensor comprises either a back-biased Hall-effect sensor, a GMR sensor, an eddy current sensor, an optical sensor or a capacitive sensor.

5. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 1, wherein at least one said proximity sensor comprises a switch, said switch is adapted to engage the anchor bolt, and a state of said switch is responsive to whether or not said anchor bolt is engaged with the anchor bolt.

6. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt, comprising:

a. a bracket, wherein said bracket is adapted to operatively couple to one of a webbing of a seat belt and the anchor bolt, and said bracket comprises a first opening adapted to accept the other of the anchor bolt and the webbing of the seat belt;

b. a first carriage, wherein said bracket and said first carriage are adapted for said first carriage to slide relative to said bracket in a first direction or in a direction opposite to said first direction, and said first carriage comprises a second opening that cooperates with said first opening and is adapted to operatively engage said other of the anchor bolt and the webbing of the seat belt, whereby a tension in the seat belt reacted by the anchor bolt causes said first carriage to move in said first direction relative to said bracket;

c. at least one first spring operative between said first carriage and said bracket, wherein said at least one first spring is adapted to bias said first carriage relative to said bracket in a direction opposite to said first direction;

d. at least one second spring operative between said first carriage and said bracket, wherein said at least one second spring is adapted to bias said first carriage in said first direction relative to said bracket, and said first and second springs are adapted so as to substantially eliminate slack between said first carriage and said first and second springs; and

e. a first displacement sensor adapted to measure a displacement of said first carriage relative to said bracket.

7. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 6, wherein said bracket is adapted to operatively couple to the anchor bolt, and said second opening is adapted to operatively engage the webbing of the seat belt.

8. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 6, wherein said bracket is adapted to operatively couple to the webbing of the seat belt, and said second opening is adapted to operatively engage the anchor bolt.

9. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 6, wherein at least one said first spring comprises a first compression spring, and said first carriage comprises a first spring guide adapted to laterally constrain at least a portion of said first compression spring.

10. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 9, wherein said spring guide comprises a first cavity in said first carriage, a portion of said first compression spring is located within said first cavity, and a depth of said first cavity is greater than a fully compressed length of said first compression spring.

11. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 6, wherein at least one said second spring comprises a second compression spring, and said first carriage comprises a second spring guide adapted to laterally constrain at least a portion of said second compression spring.

12. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 11, wherein said spring guide comprises a second cavity in said first carriage, and a portion of said second compression spring is located within said second cavity.

13. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 6, wherein said first displacement sensor comprises:

a. a first magnetic sensor operatively coupled to said bracket;

b. a first magnet operatively coupled to said first carriage, wherein a north pole of said first magnet is located in said first direction relative to a south pole of said first magnet; and

c. a second magnet operatively coupled to said first carriage, wherein a south pole of said second magnet is located in said first direction relative to a north pole of said second magnet, wherein said first magnetic sensor is located between said first and second magnets.

14. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 13, wherein said first magnetic sensor is selected from a Hall-effect sensor and a GMR sensor.

15. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt, comprising:

a. a bracket, wherein said bracket is adapted to operatively couple to one of a webbing of a seat belt and the anchor bolt, and said bracket comprises a first opening adapted to accept the other of the anchor bolt and the webbing of the seat belt;

b. a first carriage, wherein said bracket and said first carriage are adapted for said first carriage to slide relative to said bracket in a first direction or in a direction opposite to said first direction, and said first carriage comprises a second opening that cooperates with said first opening and is adapted to operatively engage said other of the anchor bolt and the webbing of the seat belt, whereby a tension in the seat belt reacted by the anchor bolt causes said first carriage to move in said first direction relative to said bracket;

c. at least one first spring operative between said first carriage and said bracket, wherein said at least one first spring is adapted to bias said first carriage relative to said bracket in a direction opposite to said first direction; and

d. a first displacement sensor adapted to measure a displacement of said first carriage relative to said bracket, wherein said first displacement sensor comprises;

;

i. a first magnetic sensor operatively coupled to said bracket;

ii. a first magnet operatively coupled to said first carriage, wherein a north pole of said first magnet is located in said first direction relative to a south pole of said first magnet; and

iii. a second magnet operatively coupled to said first carriage, wherein a south pole of said second magnet is located in said first direction relative to a north pole of said second magnet, wherein said first magnetic sensor is located between said first and second magnets.

16. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 15, wherein said bracket is adapted to operatively couple to the anchor bolt, and said second opening is adapted to operatively engage the webbing of the seat belt.

17. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 15, wherein said bracket is adapted to operatively couple to the webbing of the seat belt, and said second opening is adapted to operatively engage the anchor bolt.

18. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 15, wherein at least one said first spring comprises a first compression spring, and said first carriage comprises a first spring guide adapted to laterally constrain at least a portion of said first compression spring.

19. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 18, wherein said spring guide comprises a first cavity in said first carriage, a portion of said first compression spring is located within said first cavity, and a depth of said first cavity is greater than a fully compressed length of said first compression spring.

20. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 15, wherein said first magnetic sensor is selected from a Hall-effect sensor and a GMR sensor.

21. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt, comprising:

a. a bracket, wherein said bracket is adapted to operatively couple to one of a webbing of a seat belt and the anchor bolt, and said bracket comprises a first opening adapted to accept the other of the anchor bolt and the webbing of the seat belt;

b. a first carriage, wherein said bracket and said first carriage are adapted for said first carriage to slide relative to said bracket in a first direction or in a direction opposite to said first direction, and said first carriage comprises a second opening that cooperates with said first opening and is adapted to operatively engage said other of the anchor bolt and the webbing of the seat belt, whereby a tension in the seat belt reacted by the anchor bolt causes said first carriage to move in said first direction relative to said bracket;

c. a second carriage, wherein said first carriage and said second carriage are adapted for said second carriage to slide relative to said first carriage within said second opening in said first direction or in said direction opposite to said first direction, and said first carriage comprises a third opening that cooperates with said first and second openings and is adapted to engage said other of the anchor bolt and the webbing of the seat belt, whereby a tension in the seat belt reacted by the anchor bolt causes said second carriage to move in said first direction relative to said first carriage.

d. at least one first spring operative between said first carriage and said bracket, wherein said at least one first spring is adapted to bias said first carriage relative to said bracket in a direction opposite to said first direction;

e. at least one third spring operative between said first and second carriages, wherein said at least one third spring is adapted to bias said second carriage relative to said first carriage in a direction opposite to said first direction;

f. a first displacement sensor adapted to measure a displacement of said first carriage relative to said bracket; and

g. a second displacement sensor adapted to measure a displacement of said second carriage relative to said bracket.

22. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 21, further comprising at least one second spring operative between said first carriage and said bracket, wherein said at least one second spring is adapted to bias said first carriage in said first direction relative to said bracket, and said first and second springs are adapted so as to substantially eliminate slack between said first carriage and said first and second springs.

23. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 21, further comprising at least one fourth spring operative between said first and second carriages, wherein said at least one fourth spring is adapted to bias said second carriage in said first direction relative to said first carriage, and said third and fourth springs are adapted so as to substantially eliminate slack between said second carriage and said third and fourth springs.

24. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 21, wherein said bracket is adapted to operatively couple to the anchor bolt, and said third opening is adapted to operatively engage the webbing of the seat belt.

25. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 21, wherein said bracket is adapted to operatively couple to the webbing of the seat belt, and said third opening is adapted to operatively engage the anchor bolt.

26. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 21, wherein said first displacement sensor comprises:

a. a first magnetic sensor operatively coupled to said bracket;

b. a first magnet operatively coupled to said first carriage, wherein a north pole of said first magnet is located in said first direction relative to a south pole of said first magnet; and

c. a second magnet operatively coupled to said first carriage, wherein a south pole of said second magnet is located in said first direction relative to a north pole of said second magnet, wherein said first magnetic sensor is located between said first and second magnets.

27. A seat belt tension sensor adapted to operatively couple to a vehicle frame with an anchor bolt as recited in claim 21, wherein said second displacement sensor comprises:

a. a second magnetic sensor operatively coupled to said bracket;

b. a third magnet operatively coupled to said second carriage, wherein a north pole of said third magnet is located in said first direction relative to a south pole of said third magnet; and

c. a fourth magnet operatively coupled to said second carriage, wherein a south pole of said fourth magnet is located in said first direction relative to a north pole of said second magnet, wherein said second magnetic sensor is located between said third and fourth magnets.