Testing the dynamic performance of seat belt pretensioners
Publication Date: 2007-Mar-07
The IP.com Prior Art Database
To better understand the performance of pretensioners at a component level prior to testing in a vehicle crash scenario, an energy absorption device is used to simulate the load curve seen by the pretensioner as it deploys. The proposals include the use of peel straps riveted to opposite sides of a constraining tube, the ends of each strap being bent to form a J shaped profile and joined to a tensioning strap which is in turn connected to a seat restraint pre-tensioner actuator. Also proposed is a hydraulic cylinder acting as a dashpot and a tapered cylinder with a plunger which plastically deforms (expands) the cylinder.
e r r s s .
Seat belt pretensioners are a standard feature in most vehicle crash systems. There is a requirement to better understand the performance of pretensioners at a component level prior to integrating them and testing them in a vehicle 'system' level crash scenario. The performance output of a pretensioner is required in order to improve the predictive CAE modelling of the seat belt and overall crash.
Currently very little is understood from a CAE perspective about the performance of pretensioners. All current component tests used to correlate with CAE are flawed in either the data that they are able to generate or in the system interactions that distort the output of the test.
In order to be a valid component test the pretensioner must deploy against an increasing load that is well understood and representative of an in-vehicle condition. The critical aspects are the fast deployment of the pretensioner (1-2 milliseconds), a varying load vs displacement curve (dependant on installation) and pulling against a low mass (the buckle, tongue and webbing). This makes it difficult to use high mass longer duration test devices or devices where it is not possible to model the test in CAE as the test equipment is too complex.
Any test solution must meet the following requirements:
1. be able to test varying types of pretensioner (buckle vs retractor vs different suppliers)
2. one test methodology should be useable across a supplier base and selected vehicle manufacturers to ensure that all results are comparable.
3. the equipment should be low mass to prevent distortion of the load curve
4. the equipment should be able to be modelled in CAE to replicate the test
5. the test should follow the same stroke resistance that the pretensioner would see in the vehicle.
The proposed solutions each use an energy absorption device to simulate the load curve seen by the pretensioner as it deploys. These allow compliance with all of the requirements:-
1. Each energy absorption device can be used on buckle or retractor pretensioners from any supplier
2. The energy absorption device can be easily replicated across many different applications and can be easily fabricated to a material specification anywhere in the world.