Load cell and seat occupant weight sensing system

Abstract

A load cell particularly useful for a seat occupant weight sensing system includes a liquid filled chamber and a pressure sensor providing an electric signal indicating the pressure in the liquid. Four load cells supporting a seat provide four signals that are added to determine the weight of the seat occupant. The load cell comprises two flanged conical springs stressed to provide preload. One of the springs also forms part of the surface of the liquid filled chamber. The two springs operate in concert to resist side forces and moments. The load cell is responsive to both compressive and tensile forces while being substantially unaffected by lateral forces and moments. A seat belt tension sensor may be included to measure seat belt tension. Preferred manufacturing methods provide low cost,

Description

FIELD OF THE INVENTION [0001] This invention relates to systems that ascertain what is occupying a vehicle seat to assist in determining optimum airbag deployment. BACKGROUND OF THE INVENTION [0002] Airbags of occupant protection systems are expensive and in certain circumstances are dangerous. It is, therefore, worthwhile to prevent deploying an airbag into an empty seat to save repair cost. It is important to avoid deployment when circumstances do not warrant deployment or when deployment might do more harm than good. It is particularly important to deploy the airbag judiciously when the seat is occupied by a child or by a very small adult. Current law requires an occupant sensing system to reliably distinguish a 107-pound adult from a child. [0003] Occupant protection systems typically include a “sensor and diagnostic module” or “SDM” that performs functions related to sensing the severity of a vehicle crash, monitoring various components of the occupant protection system for pro...

AI Technical Summary

Benefits of technology

[0028] Further, in accordance with the aforementioned preferred embodiments of the invention, the material having a larger thermal expansion coefficient has the form of an outer sleeve. The expansion of the sleeve relative to the other metal parts causes both a relative movement between a spring and a force input member and also causes an increase in the volume available for the aforementioned liquid by expanding radially outward to provide additional space fo

Problems solved by technology

Airbags of occupant protection systems are expensive and in certain circumstances are dangerous.

If the weight is very small it may be assumed that the seat is unoccupied or occupied by a small child; in either case airbag deployment would not be desired.

Side forces have many causes: Mounting the load cell between the seat and the floor can cause side forces from diffe

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