WO2003059701A1

WO2003059701A1 - Airbag with tensioned and position latching tethers

Info

Publication number: WO2003059701A1
Application number: PCT/EP2003/000395
Authority: WO
Inventors: Gavin Hall; Roy Farrington; David Cundill; James Gagg; Ian Gibson
Original assignee: Dalphimetal Ltd.
Priority date: 2002-01-17
Filing date: 2003-01-15
Publication date: 2003-07-24
Also published as: AU2003212216A1; GB0201070D0

Abstract

A side impact airbag having tethers (20, 21, 40, 41) attached to the airbag bu first attachment means (25) for allowing the placement of the tether over the airbag (12) along a route shorter in length when packaged than when deployed and second attachment means (23) for maintaining the tension achieved by the tether during the airbag inflation. The tension that is created across the airbag by said tethers is used to hold the airbag over the windows so preventing ejection. The tension in the tethers will also act to guide the airbag into its optimum position during deployment so reducing the risk of out of position.

Description

AIRBAG WITH TENSIONED AND POSITION LATCHING TETHERS

FIELD OF THE INVENTION

The present invention is generally related to airbags that are intended for use in vehicles. The airbag protects occupants from injuries that may result from a collision or other type of accident in which the vehicle is involved.

More specifically, the invention relates to curtain airbags with tensioning means for holding the airbag in position during and after deployment, providing an additional restraining force for occupant protection, and aiding in the prevention of ejection of the occupants through the side windows in the case of a rollover.

BACKGROUND

Inflatable side curtain airbag modules that are designed to provide occupant protection to vehicle occupants during a side impact or rollover event are known in the art. They are usually mounted proximate the vehicle roof rail and concealed by the headiiner trim. In both a side impact and a rollover the airbag deploys between the occupant and the side of the vehicle. The purpose of the airbag is to reduce or eliminate any injury that could be caused by contact with an intruding object or the internal structures of the car. More specifically, the airbag is designed to store and dissipate energy from the impact. An airbag must balance two objectives. Firstly, the airbag must achieve the main function of providing a means to store and dissipate energy to minimise injury. Secondly, the airbag should also be designed to minimise Out Of Position (OOP) interactions. OOP refers to possible contact between the deploying airbag and the occupant. If the occupant is in the deployment path of the curtain then he/she is Out Of Position. Out of Position is an important factor in airbag design because if the deploying curtain strikes the occupant then serious injuries can occur. The following technologies to reduce the risk of OOP are known:

The ITS (Inflatable Tubular Structure) is a product developed by Simula (USA). It is an inflatable tube of woven material, which due to the construction and orientation of the fabric weave that the material is made from, reduces in length when inflated. Thus a device stored along the upright A and C pillars and roof rail of a car, once inflated, becomes a tensioned tube containing gas, extending from A to C pillar. The device can be seen in detail on www.simula.com/asd/product.asp . This shrinkage causes longitudinal tension in the bag that reduces the risk of OOP by keeping the movement of the bag during deployment to a minimum.

A more common way of preventing OOP during deployment is to use 'loose' tethers. These are tethers which are usually attached to the edge of the curtain at one end and the vehicle, usually at the A or C pillar, at the other end. These tethers are termed 'loose' as they have no tension when the curtain is in its optimum position. The tethers are loose after deployment because their package geometry is such that they must be longer in the vehicle package than their optimum length for holding the airbag under tension after deployment. The tethers only become tensioned, by means of a tensioning force pulse, when the curtain moves a substantial distance away from its optimum position. Loose tethers cannot provide a constant tension that will restrain the occupant effectively.

Statistics show that if an occupant is ejected from the vehicle during a rollover then injuries to the occupant are usually very serious. It is therefore desirable to incorporate a system into the vehicle safety system that can prevent ejection.

It is known that modified side impact airbags can be utilised to prevent ejection. The above described 'loose' tethers have been used for such purpose so that when the airbag is deployed the tethers will hold it in position over the front and rear windows. It is also known to prevent the occupant from ejection during a rollover event or subsequent impact with a side impact airbag having a self-tensioned lower edge as described in US 6,168,191.

Another known method of preventing ejection uses the same principle described directly above but uses an uninflated material such as a plain sheet of fabric or netting instead of an airbag.

SUMMARY OF INVENTION

It is an object of this invention to provide a curtain airbag that uses the energy from the inflation of the airbag as a means to provide a constant tension across the tethers and airbag.

To accomplish this object the present invention provides a curtain airbag having multiple tethers. Tension is obtained in the tethers and airbag by ensuring that the packaged route that the tether has between the fixed end points of the tether is shorter than the deployed route between the fixed end points of the tether. The inflation energy of the bag is used to change the route of the tether during deployment.

The airbag deploys with a large vertical velocity. This gives the bag a high inertia in the vertical direction that is used to tension the tethers as described above. When the bag slows as it reaches full deployment then the inertial forces diminish which means that the tension in the tethers can act to pull the bag out of shape. To prevent this the tethers will run through one way latches. The latches allow the tether to only run one way through them. When the tethers try to run through the other way then the latches lock the tether in place. The latches will be used so that the tethers can only act to tension themselves. The latches will be positioned on the bag to ensure that the tension is directed along load paths in the bag that will not pull the bag out of shape. The latches will also ensure that the maximum tension is maintained. The airbag can also include a timed release mechanism or manual release mechanism to allow emergency exit from the vehicle past the tensioned curtain and tether. The tension that is created across the airbag by said tether arrangement can be used to hold the airbag over the windows so preventing ejection. This is because the occupant has less of a chance of getting under the curtain and the tension in the curtain also provides an additional restraining force. The tension in the tethers will also act to guide the airbag into its optimum position during deployment so reducing the risk of OOP. Tensioning the tethers means that the trajectory of the curtain will be altered in such a way as to bring it closer to the side of the car and away from the driver.

The tension also provides an additional restraining force for the occupant. The tension in the bag will mean the bag has a high positional stability.

Tensioned tethers also allow the most effective orientations of tethers to be used.

A further advantage of having a curtain with tensioned tethers is related to the field of rollover. During a rollover, which can typically last up to 7 seconds, large inertial forces can act on the curtain airbag. These forces can move the curtain airbag from its optimum position so reducing it's effectiveness. In a worst case scenario the curtain can move completely out of position and would result in it providing no protection. With tensioned tethers the curtain can be held in position and the above problem can be eliminated.

BRIEF DESCRIPTION OF DRAWINGS

The features, objects and advantages of the invention will become apparent by reading this description in conjunction with the accompanying drawings, in which:

Figure 1a is a schematic view of a vehicle with a known curtain airbag in packaged state. Figure 1b is a schematic view of a vehicle with a known curtain airbag in deployed state.

Figures 2a, 2b and 2c are schematic views of a curtain airbag with a tether arrangement according to a first embodiment of this invention. Figure 3 is a schematic views of a curtain airbag with a tether arrangement according to a first embodiment of this invention and having pipe shaped chambers.

Figures 4a, 4b and 4c are schematic views of a curtain airbag with a tether arrangement according to a second embodiment of this invention.

Figure 5 is a schematic view of a curtain airbag with a tether arrangement according to an alternate embodiment of this invention.

Figure 6 shows devices that can be used as one-way latches to lock the tethers used in the present invention in place over the airbag.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Figures 1a and 1b illustrates a known curtain airbag module 10 which comprises an airbag 12 extending from the vehicle's A-pillar 3 across the B-pillar 4 to the C-pillar 5. A plurality of fasteners 14,15 are used to secure the top 13 of the airbag 12 to the roof of the vehicle 1.

The airbag 12 is usually made of fabric or thermoplastic material and can be structured in several air chambers (not shown). An inflator (not shown) produces or supplies pressurized inflation gas to the airbag 12. Tethers 16, 17 are placed at the lower corners of the airbag 12. One end of them is bonded or sewn to the airbag corner while another end is secured to a structural portion of the vehicle in points 18, 19.

A first embodiment of the present invention as shown in Fig. 2a is a L- shaped tether arrangement. The tethers 20, 21 in this embodiment are rigidly attached to the vehicle at each end. The first end 26, 29 is attached to the upper part of the vehicle where the airbag is attached to the car under the roof trim. The second end 28, 27 is attached to the bottom section of either the A pillar or the C pillar. Each tether 20, 21 is routed over the surface of the curtain 12 through one loop 25 and one latch 23. The tether 20, 21 can pass through the loop 25 in both directions but only in one direction through the latch 23. The loop 25 and the latch 23 are fixed to the surface of the curtain 12. The operation of the curtain 12 can be explained if Figures 2b and 2c are considered (both of these figures only show one of the tethers present for clarity).

Fig 2b shows the curtain 12 in it's undeployed state. The route the tether takes can be broken down into 3 main sections: section A1 from the upper attachment point 29 to the loop 25; section B1 from the loop 25 to the latch 23; and section C1 from the latch 23 to the lower attachment point 28 at the A pillar.

Fig 2c shows the same curtain 12 but this time it is deployed. Again, the route can be broken down into the same three sections: section A2 from the upper attachment point 29 to the loop 25; section B2 from the loop 25 to the latch 23; and section C2 from the latch 23 to the lower attachment point 29 at the A pillar. It can be seen that the inflation of the curtain has changed the route the tether now takes between it's two attachment points 29, 28 via the loop 25 and the latch 23. The system will be designed so that the route A2+B2+C2 is greater than the route A1+B1+C1. By forcing the tether 20 to take a longer route after the curtain 12 is inflated tension will be achieved in the tether 20.

The loop 25 moves down relative to the car during deployment. As it does so tether 20 passes through the loop as A1 increases to A2. Drawing tether 20 through the loop 25 in turn pulls tether 20 through the one way latch 23 (from right to left). This continues to happen while the curtain 12 is inflating. When the inertial forces of the deploying curtain begin to subside the tension in the tether 20 now tries to act to pull the tether the other way through the one way latch 23 as the forces in the bag try to reach a state of equilibrium. The one way latch 23 prevents the tether 20 returning through the latch and so maintains the tension in the tether 20 and prevents the bag 12 from being pulled out of shape.

Figure 6 shows devices that can be used as one way latches like a 'cam' clamp 70, a 'fish hook' 72 or a ball bearing latch device 74.

As shown in Fig. 3 the airbag 12 may include pipe shaped chambers 30,

31 , 32 sewn into the airbag. These chambers are aligned in the horizontal and vertical directions. The chambers are designed to fill early and as they do so speed up the deployment and so provide more energy for changing the route of the tether. They also provide rigidity in the bag that helps to maintain bag shape. A second embodiment of the tensioned latching tether arrangement according to the present invention can be seen in Fig 4a. The figure shows two tethers 40, 41 criss-crossed across the surface of the bag 12.

The tethers 40, 41 are rigidly attached to the car at each end. One end 26, 29 is connected to the upper part of the vehicle where the airbag is attached to the car adjacent to the roof trim. The other end 28, 27 is attached to the bottom of either the A pillar or C pillar. Each tether 40, 41 passes through a series of loops 25 that are attached to the airbag 12 at intervals along both the top and bottom of the bag 12. Each tether 40, 41 also passes through a one way latch 23 after the series of loops 25.

To explain the operation of the bag 12 figures 4b and 4c need to be considered. As before both of these figures show only one of the tethers for reasons of clarity. Figure 4b shows an undeployed curtain 12. It can be seen that the tether 41 runs through a number of closely spaced loops 25, through a one way latch 23 and down underneath the trim of the A pillar to its attachment point

28.

Figure 4c shows a deployed curtain 12. During deployment loops 25 which were close together in the packaged form now move apart as the airbag inflates. This lengthens the route that the tether takes between its end points 28, 29. Lengthening the route the tether has to take gives the tether tension by removing all of the slack. Slack is removed as the action of the loops 25 moving apart forces tether 41 to pass through them. This embodiment has the potential to take out large amounts of slack from the tethers.

The one way latch 23 is again used to prevent the tether returning through the latch and so maintains the tension in the tether and prevents the bag 12 from being pulled out of shape.

For safety reasons the loops 25 and latches 23 will be attached to the side of the airbag which is furthest from the occupant.

The airbag can also include a maximum time delay or manual release mechanism to allow emergency exit from the vehicle past a tensioned tether.

We will now describe an alternative embodiment of the invention following Fig. 5. The airbag module includes a tether arrangement consisting of a tether or cable 50 that is rooted around a one-way loop including guides 51 , 52, 53. The tether loop is used to anchor the airbag 12 to the vehicle. The tether 50 is attached to the airbag 12 by means of a fixed attachment 54 so that during deployment the tether loop 50 is pulled through its anchor points and the loop pulls against the airbag to guide it into position. The anchor point on the vehicle 55 is positioned to hold the airbag in the correct position. This may be at the base of the B-pillar or other section of vehicle trim. There may be a loop 56 at the anchor point on the vehicle to allow the tether to move smoothly around its looped circuit. The loop may itself form the one-way mechanism to latch position or a separate component may be used as the latch with the tether loop passing through this device at some other point along its length. A 'ratchet spool' 76 (Fig. 6) with a run on/off tether may be used at the loop point, alternatively a 'cam' clamp 72, 'fish hook' 72 or ball bearing latch device 74 may be used at some other point on the tether loop. The tether loop may be packaged integral to the vehicle trim. The vehicle packaged tether length can include an additional length equivalent to the deployment height of the airbag and still be tensioned during deployment.

The main features of an airbag according to this invention are the following. The longitudinal tension created by the tether arrangement is used to generate a low level restraining force for protecting the occupant, particularly in rollover events because said tension can be maintained after the inflator has exhausted all of its gas and so some restraining force remains for the duration of a long event such as a rollover accident. The tether arrangement provides continuous tensioning of the airbag.

The airbag is actively held in its deployed position against the side of the vehicle because the anchor points of the tether arrangement can be designed to hold the position in all three dimensions so there is less compromise on the positioning of the airbag due to the inefficiency of resolving only longitudinal forces. Positioning against the side of the vehicle reduces OOP risk. The tether arrangement can only move in one direction relative to the airbag deployment so it is possible to use the airbag inflator energy to both push and pull the airbag into position.

Inflation energy is used to push the airbag into position. A single source of energy is used to achieve position. Airbag design is less critical in terms of package fold and the resulting direction of deployment.

Supporting data A computer simulation of a generic car with a conventional curtain airbag such as the illustrated in Fig. 1 and dummy was constructed in order to show that conventional curtain airbags and tethers can not achieve the extra tension provided by the tether arrangements according to this invention.

In this simulation the dummy was given a trajectory that would eject the occupant through the side window of the car if the curtain airbag were not in the way. A number of simulations were run using the same curtain airbag but with different orientations of the tethers which were placed at the two lower corners of the airbag. The orientations of the tethers were from 0-90 degrees from the horizontal at 15 degree increments. Both of these tethers were tensioned using tensioning devices which displaced 100 mm along the line of the tether orientation. These tensioning devices were used to simulate the various methods of tensioning described in this disclosure.

The above simulation was also conducted for a curtain airbag where the tethers were positioned in the normal position with no tensioning device. This was to provide a baseline to which the tensioned tethers simulations could be compared. It was seen that all of the tensioned tethers curtain airbags reduced the severity of the ejection of the dummy. It was found that the tethers orientated at 30 degrees from the horizontal provided the best configuration for preventing ejection. The results for this simulation as well as the baseline simulation are shown below. Results of the 30 degree tethers simulation and the normal tethers simulation

Tether Type Displacement of the head Maximum Tether in the Y direction (m) Tension Force (N)

Normal 0.613 1706 30 degrees 0.578 3675

It can be seen that the displacement of the head in the Y direction (toward the side window) is reduced by 35 mm. Although this is a small displacement the injuries to the occupant would have been greatly reduced as the tensioned tethers would have prevented his head from passing outside of the protective structure of the car. It can also be seen that the tension in the tethers needed to restrain the occupant by the extra 35 mm is over double the normal curtain tether tension.

It can be seen that tensioned tethers help to prevent ejection of the occupant. It was found that the most effective orientation of tether was 30 degrees below the horizontal. A normal tether could not be positioned here as the packaged length of the tether would exceed the required unpackaged length. This would result in no tension in the tether.

Normal curtain airbags rely on the packaged length of the tether being shorter than the unpackaged length and also the shrinkage of the airbag as it inflates to provide tension in the tethers. It was seen that the tension needed to restrain the occupant by 35 mm was double the tension in a normal curtain airbag. This extra tension could not be realistically achieved using conventional curtain airbags and tethers.

Although the present invention has been fully described in connection with preferred embodiments, it is evident that modifications may be introduced within the scope thereof, not considering this as limited by these embodiments, but by the contents of the following claims.

Claims

1. A side impact airbag device for motor vehicles comprising an airbag (12) which is inflated by a gas provided from a gas generator in the event of an accident, said airbag (12), having the top edge secured to the vehicle structure, characterized in that further comprises at least one tether (20, 21 , 40, 41) anchored at its upper end (26, 29) at the vehicle roof and at the C and A vehicle pillars at its lower end (27, 28), said tether being attached to the airbag (12) by first attachment means (25) for allowing the placement of the tether over the airbag (12) along a route shorter in length when packaged than when deployed and second attachment means (23) for maintaining the tension achieved by the tether during the airbag inflation.

2. A side impact airbag according to claim 1 , comprising two tethers (20, 21) arranged to form each of them a L-shape between the upper anchorage

(26, 29), the bottom of the curtain and the lower anchorage (28, 27) on the vehicle, each of said tethers being attached to the airbag (12) by one of said first attachment means (25) and one of said second attachments means (23) close to said lower anchorage (28, 27).

3. A side impact airbag according to any of the preceding claims, comprising two tethers (40, 41) forming a netting arrangement around the airbag (12), each of said tethers being attached to the airbag (12) by several of said first attachment means (25) and one of said second attachments means (23) close to said lower anchorage (28, 27).

4. A side impact airbag according to any of the preceding claims wherein said first attachment means (25) are small loops that allow the tether (20, 21 , 40, 41) to slide in both directions relative to the airbag (12).

5. A side impact airbag according to any of the preceding claims, wherein said second attachment means (23) are one-way latches that allow the tether (20, 21 , 40, 41) to slide in only one direction relative to the airbag (12).

6. A side impact airbag device for motor vehicles comprising an airbag

(12) which is inflated by a gas provided from a gas generator in the event of an accident, said airbag (12) having the top edge secured to the vehicle structure characterized in that further comprises one tether loop (50) anchored at one point (55) at the B-pillar 4 of the vehicle and having guiding means (51 , 52, 53) in said pillar, said tether loop being attached to the airbag (12) by a fixed attachment (54) so that during deployment the tether loop (50) pulls against the airbag (12) to guide it into position and having an one-way latch (56) for maintaining the tension achieved by the tether loop (50) during the airbag inflation.