Hall-effect seat belt tension sensor

• US 6,205,868 B1
• Filed: 12/09/1998
• Issued: 03/27/2001
• Est. Priority Date: 12/10/1997
• Status: Expired due to Fees

• Current Assignee: Automotive Systems Laboratory, Incorporated (Ningbo Junsheng Investment Group Co., Ltd.)
• Original Assignee: Automotive Systems Laboratory, Incorporated (Ningbo Junsheng Investment Group Co., Ltd.)
• Inventors: Miller, Gregory S.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US09/208,558
• Time in Patent Office: 839 Days
• Field of Search: 324/207.26, 324/207.2, 324/235, 738/623.91, 738/624.51, 738/624.4, 280/735, 180/268
• US Class Current: 73/862.391
• CPC Class Codes: B60R 2022/4841 for sensing belt tension
• CPC Class Codes: B60R 21/0155 sensing belt tension
• CPC Class Codes: B60R 21/01556 Child-seat detection systems
• CPC Class Codes: G01D 5/147 influenced by the movement of a third element, the position of Hall device and the source of magnetic field being fixed in respect to each other

Abstract

A tension sensor (10) for a vehicle seatbelt (12) comprises a base (14) having a pair of guide pin blocks (16) and (18) depending therefrom, and a plurality of spaced upper and lower guide pins, 20 and 22 respectively, for guiding the seatbelt (12). A plunger housing (30) having an orifice (32) therein for acceptance of a movable plunger (40) is secured to the base (14). The plunger (40) has an upper portion (42) shaped to allow the seatbelt (12) to travel over the plunger (40) with minimal friction. A plurality of springs (46) are disposed between the base (14) and the plunger (40) to bias the plunger (40) against the lateral force of the seatbelt (12) when under tension. A permanent magnet (50) secured to the plunger moves into close proximity to a Hall effect sensor (52) when the plunger (40) is depressed by the seatbelt (12). The Hall effect sensor (52) has an output (54) responsive to the magnetic flux therein.

Claims

1. A tension sensor for a seatbelt comprising:

a base having first and second opposed guide pin blocks depending therefrom;

a plurality of spaced upper guide pins secured to and extending between the opposed guide pin blocks;

a plurality of spaced lower guide pins secured to and extending between the opposed guide pin blocks in spaced relation to said plurality of upper guide pins;

a plunger housing secured to said base having a plunger orifice and a plurality of detent slots therein;

a plunger disposed within the plunger orifice of said plunger housing having an upper portion shaped to allow said seatbelt to move thereacross and having a plurality of detents depending therefrom wherein the detents engage the detent slots of said plunger housing;

a plurality of springs disposed between said plunger and said base for biasing said plunger toward said upper guide pins;

a permanent magnet secured at a point to said plunger; and

a Hall effect sensor secured to said housing at a point wherein the magnetic flux of said permanent magnet varies through said Hall effect sensor when said plunger is biased toward said base, said Hall effect sensor having an output responsive to the magnetic flux therein.

4. A tension sensor for a seatbelt as claimed in claim 1 wherein the output of said Hall effect sensor is analog.

5. A tension sensor for a seatbelt as claimed in claim 1 wherein the output of said Hall effect sensor is digital.

2. A tension sensor for a seatbelt comprising:

an upper housing having a pair of spaced, integral seatbelt guides depending therefrom;

a lower housing secured to said upper housing having a pair of spaced, integral seatbelt guides depending therefrom, the seatbelt guides lying in spaced relation to the seatbelt guides of said upper housing;

a plunger housing depending from said lower housing between the seatbelt guides thereof, said plunger housing having an orifice therein defined by a housing lip portion;

a plunger disposed within the orifice of said plunger housing having an upper portion shaped to allow said seatbelt to move thereacross and a lower portion having a lip depending therefrom that engages the plunger housing lip portion thereby securing said plunger in said plunger housing;

a plurality of springs disposed between said plunger and said lower housing for biasing said plunger toward said upper housing;

a permanent magnet secured at a point to said plunger; and

a Hall effect sensor secured to said lower housing at a point wherein the magnetic flux of said permanent magnet varies through said Hall effect sensor when said plunger is biased toward said lower housing, said Hall effect sensor having an output responsive to the magnetic flux therein.

6. A tension sensor for a seatbelt as claimed in claim 2 wherein the output of said Hall effect sensor is analog.

7. A tension sensor for a seatbelt as claimed in claim 2 wherein the output of said Hall effect sensor is digital.

3. A tension sensor for a seatbelt comprising:

a base having a pair of spaced seatbelt guides, each having a slot therein for acceptance of said seatbelt;

a right circular cylindrical plunger housing having an open upper end and a lower end secured to said base between the pair of seatbelt guides, said housing having a plurality of detent slots therein;

a plunger having an upper portion shaped to allow said seatbelt to move thereacross and a right circular cylindrical lower portion having a plurality of detents depending therefrom, the lower portion disposed within said plunger housing wherein the detent slots thereof are engaged by the detents of said plunger lower portion;

a belleville spring disposed between said plunger lower portion and said base for biasing said plunger upwardly, away from said base;

a permanent magnet secured at a point to said plunger; and

a Hall effect sensor secured at a point to said base wherein the magnetic flux of said permanent magnet varies through said Hall effect sensor when said plunger is biased toward said base, said Hall effect sensor having an output responsive to the magnetic flux therein.

8. A tension sensor for a seatbelt as claimed in claim 3 wherein the output of said Hall effect sensor is analog.

9. A tension sensor for a seatbelt as claimed in claim 3 wherein the output of said Hall effect sensor is digital.