Gas bag restraint system for vehicle occupants

Details Gas bag restraint system for vehicle occupants Gas bag restraint system for vehicle occupants

1998-07-23

2001-03-06

Johnson, Brian L. (Department: 3618)

Land vehicles

Wheeled

Attachment

C280S743100

Reexamination Certificate

active

06196575

ABSTRACT:

TECHNICAL FIELD
The invention relates to a gas bag restraint system for vehicle occupants.
BACKGROUND OF THE INVENTION
From German Patent DE 29 44 319 A1 a gas bag restraint system is known with a gas bag which can take up various volumes depending on the intensity of the impact. In the non-unfolded state, two chambers are provided, with a tear seam connecting opposite sections of the outer wall with each other. Thereby, only one chamber can be inflated when the interior pressure of the gas bag is not sufficient to destroy the tear seam. In the case of a collision with high impact intensity, the internal pressure in the gas bag is increased so that the tear seam is destroyed and the gas bag can take up a greater volume. In this case, not two chambers are formed, but rather one large chamber is produced. A problem of the gas bags known hitherto consists in that the abruptly unfolding gas bag strikes against an occupant sitting close to the restraint system and not yet moving forward relative to the vehicle. In addition, in fully inflated state when the occupant falls into it, the gas bag is relatively hard.
A further gas bag restraint system is shown in the DE 92 11 421 U1. This gas bag restraint system comprises a gas bag with two chambers, one chamber, namely the greater of the two, offering protection at the primary impact of the vehicle occupant and thereafter collapsing relatively quickly. The second chamber, on the other hand, collapses distinctly later than the first chamber, so that in the case of a secondary impact the vehicle occupant does not hit against hard parts such as the gas generator. In this known restraint system, always both chambers are unfold. Valve flaps on the dividing wall between the first and the second chamber permit a passage of gas exclusively from the first into the second chamber.
BRIEF SUMMARY OF THE INVENTION
The invention provides a gas bag restraint system, in which the unfolding gas bag, when the occupant is sitting relatively close to the gas bag restraint system, strikes onto the occupant with lower force. In addition, when the occupant falls into the gas bag, the gas bag is not as hard as the previous gas bags so that the risk of injury as a whole can be reduced. The gas bag restraint system according to the invention comprises a gas bag with an interior having a first and a second chamber. The gas bag has an outer wall delimiting the interior of the gas bag and at least one dividing wall in the interior for separating the first and the second chambers in the fully inflated state of the gas bag. The dividing wall is gas-permeable at least while the gas bag is inflating to reach a fully inflated state of the gas bag. The system further comprises a multiple-stage gas generator which is communicated with the first chamber and which is able to produce different internal pressures of the gas bag.
Thereby, it can be achieved that one chamber or both chambers are inflated. On inflating of both chambers, the second chamber, however, is inflated with a delay, which distinctly reduces the risk of injury, without restricting the restraining effect. The dividing wall can be gas-permeable only upon reaching a predetermined internal gas bag pressure, e.g. by providing openings with a valve function, or can be permanently open, e.g. by a dividing wall of a gas-permeable material.
The invention is based on the knowledge that the above-mentioned disadvantages can be effectively prevented by a delayed inflating of the gas bag. Whereas in the prior art German Patent DE 29 44 319 A1 the tear seam is destroyed abruptly and the single large chamber which is then formed is inflated suddenly, in the gas bag restraint system according to the invention a dividing wall is always provided, which divides the interior of the gas bag into several chambers. If not only the first but also the second chamber is to be inflated, the dividing wall provides for that the gas flow from the first into the second chamber is throttled and the second chamber is inflated with a delay in relation to the first chamber. Single-chambered gas bags which were usual hitherto are already completely filled after approximately 39 ms. On the other hand, the gas bag according to the invention is only filled after approximately 42 ms or later, whereby a slower pressure rise is produced in its interior.
The dividing wall can have at least one through-flow opening and/or be of a gas-permeable material.
Preferably, holding means are provided which prevent an unfolding of the part of the outer wall delimiting the second chamber before reaching the predetermined internal pressure of the gas bag, and which permit the full inflation of the second chamber after the predetermined internal pressure of the gas bag has been reached.
In the preferred embodiment, the multiple-stage generator produces gas in at least two stages which are identical in terms of output and which are able to be activated separately from each other, whereby, as tests have shown, a good evolution of the pressure over the time is produced in the interior of the gas bag. Moreover, stages which are differing with respect to output can also be provided. So that the energy arising on ignition of the propellant charges is not released too abruptly and so that the pressure rise does not occur too suddenly, a control unit, which is coupled with sensors and with the gas generator, can ignite provided ignition units in a manner staggered in time with respect to each other. Thus, a gradual evolution of pressure is produced.


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