WO1998054032A1

WO1998054032A1 - Airbag with blast shield

Info

Publication number: WO1998054032A1
Application number: PCT/US1998/009507
Authority: WO
Inventors: Daniel Edward Bartoldus
Original assignee: Breed Automotive Technology, Inc.
Priority date: 1997-05-30
Filing date: 1998-05-12
Publication date: 1998-12-03

Abstract

A vehicle occupant restraint assembly (10) has an airbag (20) and an inflator (40) having a gas exhaust port (46) for inflating the airbag (20). The vehicle occupant restraint assembly (10) also has a blast shield (60) positioned between the airbag (20) and the gas outlet port (46) of the inflator (40) thereby protecting the airbag (20) from the gas being discharged from the inflator (40). The blast shield (60) is preferably made of a flexible thermoplastic. To construct a vehicle occupant restraint assembly (10), the inflator (40) is placed inside the airbag (20). The blast shield (60) is positioned between the gas exhaust port (46) of the inflator (40) and the airbag (20).

Description

AIRBAG WITH BLAST SHIELD

This invention pertains generally to vehicle occupant restraints, such as airbags, and more specifically to methods and apparatuses for protecting an airbag from the gas discharged from an inflator. It is well known to provide vehicle occupant restraint assemblies for vehicles such as passenger cars to restrain a vehicle occupant during a crash. Vehicle occupant restraint assemblies typically include an airbag, an inflator and a retainer or module housing used to attach the airbag to the inflator. However, a vehicle occupant restraint assembly, such as the one disclosed herein, may not require a retainer or module housing. In either case, when a vehicle crash is sensed the inflator inflates the airbag with a pressurized gas, restraining the associated vehicle occupant.

A problem in the art is the damage that can be done to the airbag by the pressurized gas that is discharged from the inflator. As the vehicle occupant restraint assembly deploys, gas exits the inflator and enters the airbag at high pressure and, in some cases, high temperature. The high pressure can cause holes to form in the airbag as the gas separates the yarns which were knitted or woven together to form the fabric used to make the airbag. In cases of high temperature, the gas may melt the airbag fabric as it passes through the newly formed holes. These holes let the gas escape the inflation chamber of the airbag thereby reducing the designed effectiveness of the vehicle occupant restraint assembly and increasing performance variability. In some cases, the holes may cause a complete failure (i.e., tearing) of the vehicle occupant restraint assembly and increasing performance variability. In some cases, the holes may cause a complete failure (i.e., tearing) of the airbag. This problem is most common when a hybrid inflator is used. Hybrid inflators combine the use of a gas-generating material and a quantity of stored gas. The gas is typically stored at a very high pressure i.e., 204 to 408 Atmospheres. The gas- generating material is typically combustible and ignitable and thus the gas discharged to the airbag may have a high temperature.

The present invention provides methods and apparatuses for reducing the damage done to airbags by inflation gas. Thus, the difficulties inherent in the prior art are overcome in a way that is simple and efficient while providing better and more advantageous results .

BRIEF DESCRIPTION OF THE INVENTION

The invention may take physical form in certain parts and arrangement of parts, a preferred embodiment of which will be described in detail in this specification and illustrated in the accompanying drawings which form a part hereof and wherein:

FIGURE 1 is a perspective view of the vehicle occupant restraint assembly of the present invention showing the airbag in a folded configuration.

FIGURE 2 is a side elevation view of a hybrid airbag inflator that may be employed in the present invention .

FIGURE 3 is a fragmentary front view of the airbag in an unfolded, uninflated configuration.

FIGURE 4 is a fragmentary sectional bottom view taken along the line 4-4 of FIGURE 3 showing the diffuser region of the airbag.

FIGURE 5 is a fragmentary sectional view taken along the line 5-5 of FIGURE 3.

FIGURE 6 is a fragmentary sectional view taken along the line 6-6 of FIGURE 3.

DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein the showings are for purposes of illustrating a preferred embodiment of the invention only and not for purposes of limiting the same, FIGURE 1 shows a vehicle occupant restraint assembly 10 for use with an associated vehicle. The embodiment illustrated is intended for use in vehicles designed with side mounted side impact airbags and the invention is applicable to airbags used for driver side, passenger side, and other applications as well. The occupant restraint assembly includes an airbag 20, an inflator 40 and a blast shield 60 (shown in FIGURES 4 and 5) . In FIGURE 1 the airbag 20 is shown in a folded configuration as when the airbag is being installed into an associated vehicle (not shown) . In FIGURE 3 a fragmentary view of the airbag 20 is shown in an unfolded, uninflated configuration. As can be seen in FIGURE 1, the inflator 40 is positioned within the airbag.

With reference now to FIGURE 2, the inflator 40 has first and second ends 41, 43. In this embodiment the inflator is an inflator known in the art as a hybrid inflator, but other types of inflators could also be used in the practice of this invention. A hybrid inflator, as discussed above, is one that combines the use of a gas-generating material and a quantity of stored pressurized gas to inflate the airbag. The inflator 40 has a pressure vessel 42 that contains a suitable pressurized gas 44 and a diffuser housing 45 with gas exhaust ports 46 that allow the pressurized gas and gas generated by a gas-generating material to leave the inflator and enter the airbag. The gas exhaust ports 46 are preferably circular with a diameter D5. The diffuser housing 45 is preferably circular in cross section with a diameter D6 and a circumference Cl. The hybrid inflator 40 also has an igniter assembly 48 that is used to operate the inflator. The igniter assembly 48 is selectively connectable to an electrical contact means 49 that connects the igniter assembly to a crash sensor (not shown) or a controller (not shown) . The crash sensor can be of any type presently used in the art to sense a collision or sudden deceleration of the associated vehicle .

With reference now to FIGURES 1, 3 and 4, the airbag 20 is made of a sheet material 22 that is preferably sewable nylon but other materials chosen with sound engineering judgement could also be used. This invention is applicable to airbags wherein the sheet material is woven, knitted or a film. It is well known in the art to coat the airbag material with a substance such as silicone to reduce gas leakage. This invention is applicable for airbags comprising both coated and un-coated sheet materials. A possible advantage is available, however, when the airbag is un-coated, as will be discussed below. The sheet material 22 is sewn together with any thread 24 chosen according to sound engineering judgement, such as nylon thread, thereby forming seams 23. It should be noted that the seams 23 in FIGURES 1 and 3 are shown as single seams. By single seams it is meant that only one line of thread 24 is used to form the seam. This is done to simplify the figures. Though single seams are possible with this invention, preferably, the seams are double seams, i.e., have two lines of thread. The seams 23, 23a, 23b in FIGURE 4, 5 and 6 are shown as double seams. With reference now to FIGURES 1, 3-5 and 6, the airbag 20 of this preferred embodiment has a gas retaining portion 26 that is bordered by first and second outer flaps 28, 29 and a horizontally spaced portion of the seam 23 labeled as 23a in FIGURE 3. It is understood that modifications may be made to the airbag design. For example, the first and second outer flaps 28, 29, are not required for the practice of this invention. The gas retaining portion 26 of the airbag 20 is used to contain the gas when the airbag is inflated. The gas retaining portion 26 of the airbag, as best seen in FIGURES 5 and 6, preferably has a single layer segment 30 and a double layer segment 32. The single layer segment 30 comprises one layer of sheet material and the double layer segment 32 comprises two layers of sheet material. The single and double layer segments 30, 32 are sewn together using seams 23, 23a constructed with thread 24. The gas retaining portion 26 of the airbag has, as seen in FIGURES 3 and 4, first and second openings 34, 36 therethrough preferably located within the double layer segment 32. The peripheries of the first and second openings 34, 36 are reinforced by seams 23. It should be noted, as best seen in FIGURE 6, that the second opening 36 is located in a first wall 25 of the airbag but does not extend through a second wall 27. The first opening 34 is similarly located only in the first wall 25.

With reference now to FIGURES 1-4, the first and second openings 34, 36 in the airbag 20 are preferably circular with diameters Dl and D2 respectively. The inflator 40 has a length LI and a maximum cross-section dimension XI. Preferably the inflator 40 has a circular cross-section and thus in this preferred embodiment, the maximum cross-section dimension XI is the diameter D3 of the pressure vessel. The inflator 40 is inserted into the airbag 20 through the second opening 36 of the airbag during the installation or manufacturing process. Preferably the entire inflator is non-passable through the first opening 34. By non-passable it is meant that a force larger than a manually generated force would be required to pass the entire inflator through the first opening. Such a large force would likely rip the sheet material 22 around the first opening 34 and is undesirable. Of course the force used to insert the entire inflator 40 through the second opening 36 does not have to be manually generated but it should not require a magnitude greater than a manually generated force. Therefore the inflator 40, at its maximum cross-section dimension XI, which is preferably the diameter D3, can selectively pass through the second opening 36 but is non-passable through the first opening 34. The first end 41 of the inflator, however, has a diameter D4 and is able to be passed through the first opening 34 of the airbag so that the first end 41 can extend through the first opening 34.

With continuing reference to FIGURES 1-4, the first end 41 of the inflator extends through the first opening 34 of the airbag while the second end 43 of the inflator extends through the second opening 36 of the airbag. In this way the inflator retains the airbag without any additional components required. The centers of the first and second openings 34, 36 are spaced apart a distance L2. The size of the inflator i.e., the diameters D3, D4 and the length LI, determine the appropriate sizes for the diameters Dl, D2 , of the first and second openings 34, 36 as well as the distance L2 between the first and second openings 34, 36. Although these sizes can be any chosen with sound engineering judgment, the distance L2 is preferably within the range of 7.0 cm smaller than length LI

(length LI - 7.0 cm) to 7.0 cm longer than length LI (length LI + 7.0 cm) . Thus it can be appreciated that length LI of the inflator 40 can vary somewhat without changing the design of the airbag 20. Still referring to FIGURES 1-4, the first and second openings 34, 36 preferably have sealing means. While this invention does not require sealing means, it is preferred because without sealing means when the airbag 20 is inflated the inflation gas could leak out of the airbag through the first and second openings 34, 36. Thus the capacity of the inflator 40 would have to be greater to properly inflate the airbag, increasing the cost of the inflator. The sealing means can be any chosen with sound engineering judgment but preferably is an interference fit of the sheet material with the exterior of the inflator. To accomplish the interference fit, the diameter Dl of the first opening 34 is preferably within the range of 7.0 mm smaller than the diameter D4 of the first end 41 of the inflator 40 (diameter D4 - 7.0 mm) to 1.0 mm smaller than the diameter D4

(diameter D4 - 1.0 mm) . Similarly, the diameter D2 of the second opening 36 is preferably within the range of 7.0 mm smaller than the diameter D3 of the second end 43 of the inflator 40 (diameter D3 B 7.0 mm) to 1.0 mm smaller than the diameter D3 (diameter D3 - 1.0 mm.

With reference now to FIGURES 2, 4 and 5, a blast shield 60 is used to protect the airbag from possible damage caused by the discharge of gas through the gas exhaust ports 46 of the diffuser housing 45 when the occupant restraint assembly is deployed. The blast shield is positioned between the gas exhaust ports 46 of the diffuser housing 45 and the airbag 20 as will be explained further below. The blast shield can be formed of any material chosen with sound engineering judgement, but in this preferred embodiment the blast shield 60 is formed of a flexible thermoplastic material . A prototype of the invention has been made using a flexible thermoplastic material for the blast shield. The material used for the blast shield in the prototype is sold under the trademark Zytel 7 FN and is manufactured by DuPont of Wilmington, Delaware. Zytel 7 FN is a plasticizer-free thermoplastic flexible nylon alloy.

With reference to FIGURES 1-5, the inflator 40 of this embodiment is positioned, as noted above, the first end 41 of the inflator extends through the first opening 34 of the airbag 20 and the second end 43 of the inflator extends through the second opening 36 of the airbag. With the inflator positioned thus, the gas exhaust ports 46 of the diffuser housing 45 are located in diffuser region 17 of the airbag. Therefore, to protect the airbag 20 from discharging gas, the blast shield 60 is attached to an inside surface 15 of the airbag in diffuser region. The attaching means used to attach the blast shield 60 to the airbag may include sewing, the use of adhesives, heat stacking, as well as other attaching means known in the art. Preferably the blast shield 60 is formed of a material, such as Zytel 7 FN, that is sewable to the airbag using thread 24 to make vertically spaced seams 23b. During the construction of the occupant restraint assembly 10, the blast shield 60 is positioned such that it encircles the diffuser housing 45 of the inflator 40 thereby being disposed between the airbag 20 and the gas exhaust ports 46 of the diffuser housing.

With reference now to FIGURES 2, 4 and 5, the preferred dimensions for the blast shield 60 are as follows. The blast shield can have any shape chosen with sound engineering judgment but is preferably rectangular in shape with a thickness Tl, a width Wl and a length L3. It has been determined by experimentation that the thickness Tl of the blast shield 60 should be within the range of 0.5mm to 1mm. Preferably, the thickness Tl is 0.5mm because this provides sufficient protection for the airbag while minimizing the quantity of material required to form the blast shield. The width Wl of the blast shield 60 is preferably within the range of 5 times the diameter D5 of the gas exhaust ports of the inflator 40 (diameter D5 x 5) to 16 times the diameter D5 of the gas exhaust ports 46 (diameter D5 x 16) . For this preferred embodiment, the width Wl of the blast shield 60 is 11 times the diameter D5 of the gas exhaust ports 46

(diameter D5 x 11) . The length L3 of the blast shield should be sufficient to encircle the diffuser housing of the inflator as discussed above. Thus, the length L3 of the blast shield 60 is preferably within the range of the circumference Cl of the diffuser housing 45 (circumference Cl) to 3 times the circumference Cl (circumference Cl x 3) . For this preferred embodiment, the length L3 of the blast shield 60 is 2 times the circumference Cl of the diffuser housing 45 (circumference Cl x 2) .

With reference now to FIGURES 1-6, the vehicle occupant restraint assembly 10 is constructed in this way. The sheet material 22 is sewn together, using thread 24 to form seams 23, into the appropriate shape for the airbag 20. The peripheries of the first and second openings 34, 36 are reinforced with seams 23 and the blast shield 60 is sewn onto the inside surface 15 of the airbag. At this point the airbag 20 can be folded as is currently known in the art. The inflator 40, having a diffuser housing 45 with gas exhaust ports 46, is then inserted into the airbag through the second opening 36. The second end 43 of inflator remains extended through the second opening. Next the first end 41 of inflator is extended through the first opening 34. The diffuser housing 45 of the inflator is then encircled by the blast shield 60 so that the blast shield is positioned between the airbag and the gas exhaust ports 46 of the diffuser housing. Finally, the electrical contact means 49 is attached to the igniter assembly 48 of the inflator 40.

In an alternative embodiment of this invention, with reference to FIGURES 1 and 3-5, the sheet material 22 that is used to make the airbag is formed of yarns of the same base material as the flexible thermoplastic material used to make the blast shield 60. Preferably, the blast shield is made of Zytel 7 FN which is, as noted above, a nylon alloy and the airbag 20 is made of sewable nylon material. The use of nylon for both enables the airbag and the blast shield to be fully recyclable after the vehicle occupant restraint assembly has been deployed. It should be noted that the airbag is only recyclable if it is un-coated. This is true because coating materials known in the art, including silicone for example, are not made of the same plastic grade to be recyclable with the nylon material used to make the airbag. Thus, where an airbag has a coating, the coating would have to be separated from the airbag before recycling could properly take place. The separation of coatings from airbags is known to be an expensive procedure.

Claims

CLAIMS :

1. A vehicle occupant restraint assembly (10) for use with an associated vehicle, the vehicle occupant restraint assembly comprising: an airbag (20) ; an inflator (40) having a gas exhaust port for inflating said airbag, said inflator selectively discharging a pressurized gas through said gas exhaust port (46) into said airbag; and, a blast shield (60) for protecting said airbag, said blast shield being attached to an inside surface of the airbag and positioned between airbag and the gas exhaust port of the inflator, said inflator being at least partially located within airbag.

2. The vehicle occupant restraint assembly (10) of claim 1 wherein said blast shield (60) comprises a flexible thermoplastic material.

3. The vehicle occupant restraint assembly (10) of claim 2 wherein said airbag (20) comprises the same thermoplastic material as the blast shield (60) .

4. The vehicle occupant restraint assembly (10) of claim 3 wherein said base material is nylon.

5. The vehicle occupant restraint assembly (10) of claim 2 wherein said blast shield (60) has a thickness in the range of about 0.5 mm to 1 mm.

6. The vehicle occupant restraint assembly (10) of claim 1 wherein the blast shield (60) is attached to said airbag (20) by sewing.

7. The vehicle occupant restraint assembly (10) of claim 1 wherein said gas exhaust port (46) of said inflator (40) has a diameter D5 and said blast shield (60) has a width Wl, said width Wl being in the range of about five times diameter D5 to about sixteen times diameter D5.

8. The vehicle occupant restraint assembly (10) of claim 1 wherein said inflator (40) has a diffuser housing (45) that includes said gas exhaust port (46) , said diffuser housing having a circumference Cl and said blast shield (60) having a length L3, said length L3 being in the range of about 1 times circumference Cl to about 3 times circumference Cl.

9. The vehicle occupant restraint assembly (10) of claim 1 wherein said airbag (20) has first and second openings (34,36), said inflator having first and second ends (41,43), said first end extending through said first opening and said second end extending through said second opening.

10. The vehicle occupant restraint assembly (10) of claim 1 wherein said inflator (20) has a diffuser housing (45), said gas exhaust port (46) being located on said diffuser housing, said blast (60) shield selectively encircling said diffuser housing.