Device for inflating an airbag

Abstract: A device for inflating an airbag (9) has a gas generator (1) that produces an inflation gas. A valve control adjusts the cross-section of a flow channel (2) through which the inflation gas is supplied to the interior of the airbag by means of valve elements (3, 4). The valve elements are held in an unactivated position by holding elements (5, 6) with a holding force that is lower than the actuating force used to actuate the valve elements.

Description: The invention relates to a device for inflating an airbag according to the preamble of claim 1. A device of this type is known from US-A-4 006 919. The known device comprises a gas generator for producing a inflation gas and valve control for adjusting a cross-section of a flow channel through which the inflation gas is supplied to the interior of the airbag by means of valve elements, whereby the valve elements are held in an unactivated position by holding elements with a holding force which is lower than the actuating force used to actuate the valve elements. In the unactivated position the valve elements are held by the holding elements in a rattle-free manner. The holding elements are designed as shear pins and are sheared off by the actuating force of the pressurized gas released from the gas generator. The valve elements comprises a cylindrical sleevelike valve spool which is positioned within an elongated cylindrical sleevelike liner and fixed in the unactivated position by the shear pins. With a device known from EP 0812741 A1 the quantity of inflation gas supplied to the airbag is regulated by one or more controlled shutters being used as valve elements which are provided in the path of gas flow between the gas generator and the interior of the airbag. The quantity of inflation gas supplied to the interior of the airbag is controlled as a function of the unimpeded advance movement of the airbag into the passenger compartment. The risk of injury to a vehicle occupant located "out of position", for example in a forwardly displaced position, is thus avoided. The presence of a child seat in the path of advance movement of the airbag is also allowed for, and the quantity of inflation gas supplied to the interior of the airbag controlled accordingly. It is an object of the invention to provide a device of the type mentioned at the outset in which the actuation of the valve elements is improved for a controlled inflation of the airbag in dependence of the advance movement of the airbag into the passenger compartment. This object is achieved by the characterising portion of the claim 1. When the valve control is activated the valve elements in the form of valve flaps which can be pivoted into the cross section of flow of the inflation gas, can be actuated by pyrotechnic devices activated as a function of the desired control, by stored mechanical energy (for example springs) which is released as a function of the valve control, or by electromagnetic devices, or other suitable means. The risk that the valve elements will be moved unintentionally from the rest position by the gas stream, vibrations and the like is avoided by the holding elements designed, in particular, as shear elements, for example shear pins. The holding force of the holding elements is so designed that it is lower than the actuating force with which the valve elements are moved into the cross section of flow of the inflation gas stream by suitable actuators. However, the holding force is greater than forces exerted by the inflation gas stream on the valve elements due to turbulence, suction and the like. This ensures that even the maximum cross section of flow for the inflation gas streaming into the interior of the airbag is reliably available if there is no obstacle in the path of advance movement of the airbag as it is inflated. One valve element or a plurality of valve elements can be provided, in particular for incremental control. Noises due to rattling of the valves are avoided during normal vehicle operation, in particular, as a result of the rattle-free positioning of the valve elements. Brief Description of the Drawings An embodiment of the invention will be described in more detail hereinafter with reference to the figures, in which: FIG. 1 is a section through an embodiment; and FIG. 2 is a plan view of a valve element arrangement in its rest position. Detailed Description of the Invention FIG. 1 shows a gas generator 1 adapted to inflate an airbag 9 arranged in an airbag compartment in an undeployed state, via a flow channel 2. The gas generator 1 produces an inflation gas that is supplied to the interior of the airbag 9 through the flow channel 2. The path of advance movement of the airbag 9 as it is inflated and deployed is tracked by means of a scanner 11 such as that known from EP 0812741 A1 and described in detail in DE 29811733.9 U1. If there is an obstacle, for example a child seat or an "out of position" vehicle occupant in the in the path of advance movement of the airbag, a valve control is activated, reducing the cross section of flow of the flow channel 2 to restrict the supply of inflation gas to the airbag 9. To reduce the cross section of the flow channel, valve elements 3, 4 in the form of pivotable flaps adapted to pivot around pivot axes 10 in the flow channel 2 between the gas generator 1 and the airbag 9 are provided in the embodiment illustrated. Using correspondingly designed actuators 7, 8 which are associated with the respective valve element 3, 4, it is possible to pivot the valve elements individually or together during valve control from an inactivated position, shown in broken lines in FIG. 1 and in solid lines in FIG. 2, into the positions shown in solid lines in FIG. 1. The actuators 7, 8 can be actuated by pyrotechnic energy, mechanical energy, for example springs, or electromagnetically. The respective actuator 7, 8 can be activated by a corresponding ignition signal or actuating signal. Holding elements 5, 6, which are designed as shear pins in the embodiment illustrated, are provided to hold the valve elements 3, 4 securely in their unactivated positions. These shear pins 5, 6 are anchored in one or both lateral walls 12 of the flow channel 2, as shown in FIG. 2, for the holding element 6 designed as a shear pin. The entire cross section of the flow channel 2 is unobstructed when the valve elements are in their unactivated positions. The valve elements 3, 4 adopt this unactivated position during normal vehicle operation. The valve elements 3, 4 also adopt the unactivated position when the entire cross section of the flow channel is to be cleared for inflating the airbag 9, i.e. in the case where an unimpeded advance of the airbag into the passenger compartment is detected by the scanner 11. Stationary intake edges 12, 13 are also provided in front of the valve elements 3, 4 in the illustrated embodiment and pass over into beveled front surfaces of the valve elements 3, 4 for achieving flow behaviour of the inflation gas which is as free as possible from turbulence and pressing of the valve elements 3, 4 into the unactivated position. The holding elements 5, 6 ensure that the valve elements 3, 4 are held securely in the unactivated position. Forces acting over the entire cross section of the flow channel on the holding elements 5, 6 during normal vehicle operation or also during inflation of the airbag 9 are lower than the holding forces exerted by the holding elements 5, 6. This allows reliable positioning of the valve elements 3, 4 in the unactivated position. Actuating forces which are greater than the holding forces of the holding elements 5, 6 are liberated on activation of the actuators 7, 8. If the holding elements are designed as shear pins, the shear pins are sheared off so that the valve elements 3, 4 are pivoted individually, or together, into the flow channel 2 to reduce the cross section of the flow channel. Instead of the shear pins, projections can also be provided in the lateral walls 12 which project into corresponding recesses in the valve elements 3, 4 and impart the corresponding holding forces. Friction surfaces, which impart the corresponding restraining force, can also be provided between the lateral walls 12 and the lateral surfaces of the valve elements 3, 4.

Claims: A device for inflating an airbag comprising a gas generator for producing an inflation gas and a valve control for adjusting a cross-section of a flow channel (2) through which the inflation gas is supplied to the interior of the airbag by means of valve elements (3, 4), wherein the valve elements (3, 4) are held in an unactivated position by holding elements (5, 6) with a holding force which is lower than the actuating force used to actuate the valve elements (3, 4), characterized in that the valve elements (3, 4) have the form of pivotable flaps adapted to pivot around pivot axes (10). A device according to claim 1 characterized in that actuators (7, 8) are associated with the respective valve element (3, 4), wherein the respective actuator is activated by a corresponding actuating signal to pivot the associated valve element (3, 4) and the respective holding element (5, 6) is sheared off by the actuating force of the actuators (7, 8). The device according to claim 1 or 2 characterised in that the holding elements (5, 6) are designed as shear pins. The device according to one of claims 1 to 3 characterised in that the valve elements (3, 4) are held in a rattle-free manner in the unactivated position by the holding elements (5, 6).

Inventors: SPECHT MARTIN, SPECHT, MARTIN
Applicants: BREED AUTOMOTIVE TECH, BREED AUTOMOTIVE TECHNOLOGY, INC.
Application year: 1999
Main classification: B60R21
IPC codes: B60R21