Pretensioners and load-limiters are two well-known safety devices for seat belt systems of motor vehicles. The pretensioner is used to rapidly remove belt slack in the very early stage of a crash event. On the other hand, the load-limiter is used in the later stage of a crash event to regulate the maximum seat belt force acting on the occupant and to control the occupant forward excursion. In this paper, a linear pretensioner and load-limiter combo device is presented, which possesses the advantages of both pretensioner and load-limiter but without the corresponding packaging, mass and cost disadvantages. In this two-in-one design, the webbing displacement induced by the operation of a linear pretensioner is reused for load-limiting purposes. A mechanics model is developed to analytically estimate the load-limiting force and to understand relations among system variables and performance. Using this model, the equation of load-limiting force was derived. A prototype device was designed, built and tested to verify the validity of the model. While the linear pretensioner and load-limiter combo device is integrated into the seat belt buckle, it is also suitable to be integrated into the shoulder belt height adjuster due to its linear construction. Since the device is only the size of a buckle pretensioner, it eliminates the packaging, mass and cost associated with an additional load-limiter. For the covering abstract see ITRD E825082.
Samenvatting