Force sensor for seat occupant weight sensor

• US 6,224,094 B1
• Filed: 05/19/1998
• Issued: 05/01/2001
• Est. Priority Date: 05/19/1998
• Status: Expired due to Fees

• Current Assignee: Peter Norton
• Original Assignee: Peter Norton
• Inventors: Norton, Peter
• Primary Examiner(s): CULBRETH, ERIC D
• Application Number:
  US09/081,194
• Time in Patent Office: 1,078 Days
• Field of Search: 280/734, 280/735, 73/862.581, 73/744, 73/745, 73/746
• US Class Current: 280/735
• CPC Class Codes: B60R 21/01516 using force or pressure sensing means
• CPC Class Codes: G01G 19/4142 for controlling activation of safety devices, e.g. airbag systems electrical circuits for triggering safety arrangements in case of vehicle accidents B60R21/015
• CPC Class Codes: G01L 1/02 by hydraulic or pneumatic means

Abstract

A force sensor for sensing the weight of a vehicle seat occupant for a vehicle'"'"'s occupant protection system has a pressure sensor responsive to hydraulic pressure resulting from axial force applied to the force sensor. A constant force spring in the form of a diaphragm with two flanges simultaneous functions as a seal, a constant force bias spring, an armature support resistant to radial forces and a piston for converting force to hydraulic pressure. Two studs receive applied force. An electrical insulator is sealed to the walls of a passage inside of one of the studs to provide electrical communication while sealing against liquid leakage. A pressure sensor is mounted on the electrical insulator and connected to electrical conductors in the insulator by stitch bonding. The diaphragm resists radial movement while allowing axial movement thereby making the sensor insensitive to radial forces. By being a constant force spring the diaphragm makes the sensor insensitive to temperature variations.

Claims

1. A force sensor comprising piston means for converting applied force to hydraulic pressure in a liquid confined in a chamber and including means for sensing the pressure in said liquid, the improvement comprising:

a spring providing a constant force causing a predetermined pressure in said liquid when said applied force is absent.

2. The invention as defined by claim 1 wherein:

said piston means comprises said spring.

3. The invention as defined by claim 1 wherein:

said spring comprises a diaphragm.

4. The invention as defined by claim 3 wherein said diaphragm comprises a resilient element having a shape adapted for providing said constant force and wherein,

said chamber is defined by a body and an armature joined for relative axial movement by said diaphragm.

5. The invention as defined by claim 4 wherein:

said resilient element is unitary with inner and outer flanges and said flanges are attached by sealing means to said body and to said armature whereby said chamber is sealed against liquid leakage.

6. The invention as defined by claim 5 wherein said sealing means is a weld.

7. The invention as defined by claim 5 wherein said sealing means is a braze.

8. The invention as defined by claim 4 wherein:

said diaphragm is adapted to allow relative movement between said body and said armature in the direction of an axis and to simultaneously resist relative movement between said body and said armature in directions perpendicular to said axis.

9. The invention as defined by claim 3 and including:

a restraining cover adapted to limit stress in said diaphragm in the event said applied force becomes excessive.

10. The invention as defined by claim 1 and including:

electricity conducting means residing in a passage defined by passage surfaces extending between the interior of said chamber and the exterior of said chamber for conducting electrical signals indicating the pressure sensed by said pressure sensing means.

11. The invention as defined by claim 10 made by a process comprising:

said electricity conducting means being injection molded into an electrical insulator comprising thermoplastic injection molding material selected for providing a liquid tight seal when molded around electrical conductors, and

said electrical insulator being sealed into said passage by a process of heating said passage surfaces and placing said electrical insulator into said passage whereupon said passage surfaces cool and contract and form a liquid tight seal between said electrical insulator and said inside diameter.

12. The invention as defined by claim 10 wherein:

said electricity conducting means comprises precisely two electrical conductors, and

said means for sensing the pressure in said liquid communicates said pressure through said two electrical conductors and also obtains power for operation through said two electrical conductors.

13. The invention as defined by claim 12 wherein:

said means for sensing the pressure in said liquid communicates through said two electrical conductors by drawing current through said two electrical conductors and wherein said pressure is communicated by said current.

14. A force sensor comprising:

a body having a body surface and an armature having an armature surface,

a washer comprising spring metal and having a washer surface,

an inner attachment means integral with said washer,

an outer attachment means integral with said washer,

a liquid filled chamber defined by a chamber surface, and

means for sensing pressure of said liquid, and wherein

said chamber surface comprises said body surface, said armature surface, and said washer surface, and

one of said attachment means is sealingly affixed to said body and the other of said attachment means is sealingly affixed to said armature.

15. The invention as defined by claim 14 wherein:

said washer is adapted to cause a predetermined pressure in said liquid, said predetermined pressure being constant over a range of temperatures.

16. The invention as defined by claim 14 wherein:

said washer has an axis of rotational symmetry and said washer allows movement of said armature relative to said body in the direction of said axis and resists movement of said armature relative to said body in directions perpendicular to said axis.

17. The invention as defined by claim 16 wherein:

said washer is adapted to cause a predetermined pressure in said chamber when no force is being applied between said body and said armature.

18. The invention as defined by claim 14 wherein:

said means for sensing pressure draws electric current, and said means for sensing pressure indicates sensed pressure by controlling said electric current.

19. The invention as defined by claim 14 wherein:

a said attachment means, a said attachment means comprises a flange, and said flange is sealingly attached to said armature by welding.

20. The invention as defined by claim 14 wherein:

a said attachment means comprises a flange, and said flange is sealingly attached to said armature by brazing.

21. The invention as defined by claim 14 and including:

a restraining cover adapted to limit stress in said washer in the event of excessive axial force between said body and said armature.