Airbag device

Abstract: To provide an airbag device which can provide smooth deployment of an airbag and prevent the application of undesired load regardless of whether an obstacle exists or not. An airbag device of the present invention comprises an airbag 1 having a gas inlet 12b, an inflator 6 which spouts gas into the airbag 1 through gas inlet 12b, and a retainer 5 for fixing the airbag 1. The airbag 1 is provided with gas outlets 10a formed around the gas inlet 12b for discharging gas therethrough. Therefore, gas can escape outside of the airbag 1 so as to prevent the inner pressure of the airbag 1 from exceeding a predetermined value.

Description: The present invention relates to an airbag device in which an airbag is deployed to protect an occupant in the event of vehicle collision, according to the preamble of claim 1. More particularly, the present invention relates to an airbag device which can accomplish suitable deployment of an airbag to secure sufficient ability for restraining an occupant and which is improved on the smoothness of the deployment. It should be noted that the present invention can be applied to any airbag devices for a driver's seat, a front passenger's seat, and a rear passenger's seat and also to a side airbag device. Conventionally, in order to protect occupants in the event of vehicle collision, airbag devices for a driver's seat and a front passenger's seat have been employed. Fig. 7 is a view showing an airbag, in its fully deployed state, of a typical airbag device which has been conventionally used. The airbag device includes an airbag 51 comprising a front panel 55 and a rear panel 56, and an inflator 53 which spouts gas into the airbag 51. The rear panel 56 of the airbag 51 is provided with a gas inlet 52 through which gas is spouted from the inflator 53 and vent holes 54 for discharging gas from the inside of the airbag 51. The inflator 53 is attached to a portion around the gas inlet 52 of the rear panel 56 by way of a retainer (not shown). In the conventional airbag device structured as mentioned above, gas is spouted from the inflator 53 in the event of vehicle collision. The gas enters into the airbag 51 through the gas inlet 52 so as to deploy the airbag 51. On the other hand, a part of the gas is gradually discharged through the vent holes 54. When the head or body of an occupant collides with the airbag 51, the gas within the airbag escapes outside through the vent holes 54 so that the airbag shrinks, thereby absorbing kinetic energy of the occupant. Furthermore, after a short period of time, the airbag shrinks so as to recover the field of vision for the occupant. The closest prior art document EP-A-638,466 relates to a device for controlling the rate at which gas is exhausted from an airbag cushion which is used in passenger vehicles. A dynamic vent that is impermeable to gas below a critical temperature and is permeable to gas above a critical temperature is incorporated into the material from which the airbag is made. The dynamic vent provides additional venting of gas during a high impact collision or when a larger than average occupant impacts onto the airbag cushion. US-A-5,501,488 relates to an airbag having two modes of deployment. In the normal mode, with a driver in the normal seated position, the airbag is fully deployed and inflated to attain its full normal reach and provide a cushion for protection of the driver in a collision. In the other mode, when a driver is too close to the airbag at the moment of collision, the airbag will deploy only to a shorter reach and thus protect the two close driver from being forcibly pushed backwards by the airbag inflating to its full normal reach. US-A-5,669,628 relates to an airbag cushion with a controlling doubler to provide occupant protection during both normal and out of position deployment having an enlarged gas permeable area for venting inflation gases. An obstruction to full deployment, such as a person against the steering wheel, causes venting through the enlarged area to be maintained thereby to prevent a full pressure built up which may cause injury to such person as he is pushed out of the way as the cushion deploys. Displacement of the face panel beyond a predetermined position releases a hinge mountened flap of gas impermeable material which seals off the portion of the gas permeable area that is in access of the venting needed for a normal deployment. The flap is propelled to a closing position by the inflation gas during deployment. US-A-5,743,558 relates to an aircushion module with rotating vent ring. The rotating vent ring moves to open one or more vents of different flow areas which allow inflation gas to vent to the atmosphere thereby controlling the pressure with which the inflatable air cushion fills. The rotating vent ring has a neutral or non rotated position wherein the venting is minimised such that the inflatable air cushion fills with a maximum pressure. The rotating vent ring is rotated to a variety of positions in response to one or more changing environmental conditions within the vehicle. However, the conventional airbag device has the following problems. There are possibilities that the airbag starts its deployment even when there is any obstacle to disturb the enough deployment of the airbag. In this case, as the airbag is deployed toward the obstacle in a state where a portion around the vent holes of the airbag is not completely deployed, undesired load may be applied because the vent holes for gas leak are blocked. The present invention was made in order to solve the above problem and the object of the present invention is to provide an airbag device which is improved on the smoothness of the deployment and makes it possible to prevent the application of undesired load. This object is achieved with the features of the claim 1. An airbag device according to the present invention is characterized in that the airbag is provided with gas outlets formed around the gas inlet wherein the gas outlets are torn to allow the gas to be discharged when the pressure in the airbag reaches a predetermined value. The gas outlets which are torn to allow the gas to be discharged when the pressure in the airbag reaches a predetermined value are provided, thereby controlling the deployment pressure under a predetermined value. In this embodiment, the gas outlets of the airbag may be composed of cut portions and a seam of a predetermined strength and a portion around the gas inlet may be composed of plural base fabrics and the gas outlets or the cut portions may be formed in some of the base fabrics. The deployment pressure of the airbag can be controlled by the number or the strength of the base fabrics in which the gas outlets or the cut portions are formed. An airbag device according to a second embodiment of the present invention is characterized in that the retainer is provided with gas outlets which are broken to allow the gas to be discharged when the pressure in the airbag reaches a predetermined value. As structured above, the deployment pressure of the airbag can be controlled by the breaking strength of the retainer. An additional advantage by forming the gas outlets in the retainer not in the airbag is that the requirement of providing gas outlets in the airbag can be eliminated. An airbag device according to a third embodiment of the present invention is characterized in that a space is formed between the inflator and the gas inlet of the airbag and a passage is formed between the retainer and the airbag so that the gas is discharged through the space and the passage. Since the space is formed between the inflator and the airbag and the passage is formed between the retainer and the airbag, the gas escapes outside the airbag through the space and the passage so as to prevent the inner pressure of the airbag from exceeding the predetermined value. An additional advantage of this structure is that the requirement of providing gas outlets in the airbag can be eliminated. Hereinafter, the present invention will be described with reference to attached drawings. Fig. 1 is a view showing an airbag device according to the prior art. Fig. 2 is a sectional view of the airbag device shown in Fig. 1, illustrating the state in which an airbag is deployed. Fig. 3 is a partial schematic view of an airbag of an airbag device according to the present invention, this view being taken in a direction from the inside of the airbag toward the rear panel. Figs. 4(a), 4(b) show an embodiment of a ring used in the airbag device shown in Fig. 3. Figs. 5(a), 5(b) show an embodiment of spacers used in the airbag device of the present invention. Figs. 6(a), 6(b) show embodiments of spacers used in the airbag device of the present invention. Fig. 7 is a view showing a conventional airbag device. Fig. 1 is a view showing an airbag device according to the prior art. The airbag device includes an airbag 1 comprising a front panel 2 and a rear panel 3, a ring 4, a retainer 5 and an inflator 6. The airbag 1 is made by sewing the front panel 2 and the rear panel 3 together at the peripheries thereof. The front panel 2 and the rear panel 3 are each made of plural pieces of textile fabrics (basic fabrics). The ring 4 is situated between the front panel 2 and the rear panel 3, i.e. inside the airbag 1, and functions for fixing the rear panel 3 of the airbag 1 to the retainer 5. The rear panel 3 is provided with vent holes 7 formed near the periphery thereof, holes 8a through which screws 9 of the ring 4 are inserted, gas outlets 10a, and a gas inlet 12b. The retainer 5 is provided with holes 8b positioned corresponding to the holes 8a of the rear panel 3, through which the screws 9 of the ring 4 are inserted, and gas outlets 10b for discharging gas, positioned corresponding to the gas outlets 10a of the rear panel 3. The retainer 5 also has holes 11 on the both side thereof for connecting the airbag device to a module cover (not shown). The inflator 6 is provided with holes 8c, positioned corresponding to the holes 8a of the rear panel 3 and the holes 8b of the retainer 5, through which the screws 9 of the ring 4 are inserted, and also provided with gas outlets 19 through which gas is spouted for deploying the airbag. Further, the ring 4 and the retainer 5 are provided with inflator insertion openings 12a and 12c positioned corresponding to the gas inlet 12b of the rear panel 3 and formed in substantially the center thereof, respectively. A portion including the gas outlets 19 of the inflator 6 enters inside the airbag 1 through the inflator insertion openings 12a and 12c. The holes 8a and 8b are situated around the gas inlet 12b and the inflator insertion opening 12c. The gas outlets 10a are situated around the gas inlet 12b and the holes 8a and the gas outlets 10b are situated around the inflator insertion opening 12c and the holes 8b. As mentioned above, the peripheries of the front panel 2 and the rear panel 3 are sewed up, thus forming the airbag 1. The screws 9 of the ring 4 are inserted from the inside of the airbag 1 through the holes 8a of the rear panel 3, the holes 8b of the retainer 5, and the holes 8c of the inflator 6 and nuts (not shown) are then screwed onto the ends of the screws 9 outside of the device. In this manner, the airbag device of this embodiment is constructed. The airbag device is fixed to the module cover (not shown) by screws or bolts inserted into the holes 11 provided on the both sides of the retainer 5. Fig. 2 is a sectional view of the airbag device shown in Fig. 1, with the airbag 1 being in the deployed state. The airbag device is accommodated in the module cover 17 and is fixed to the module cover 17 by the screws 13 inserted into the holes 11. To deploy the airbag 1 of the airbag device in the event of vehicle collision, gas is spouted from the gas outlets 19 of the inflator 6. As the gas is spouted from the gas outlets 19 of the inflator 6, the airbag 1 starts to be inflated with gas pressure. The airbag 1 during the inflation presses the rear surface of the module cover 17 so that tear line 14 formed in the occupant-side surface of the module cover 17 is torn by the airbag 1. After that, the airbag 1 is further largely deployed. When the obstacle 15 is too close to the airbag device as shown in Fig. 2, the airbag 1 can not be fully deployed and comes in contact with the obstacle 15 to apply the pressure. If vent holes 7 (Fig. 1) are, at this point, situated at a portion not deployed yet (still rolled and/or folded) 16 or a contact portion 18 with the module cover 17, the inner pressure of the airbag 1 can not be controlled because gas is not discharge through the vent holes 7 (Fig. 1), thereby increasing the inner pressure of the airbag 1. However, in the airbag device of this embodiment, gas escapes outside through the gas outlets 10a, 10b of the rear panel 3 and the retainer 5, positioned around the periphery of the inflator 6, thereby preventing the inner pressure of the airbag 1 from exceeding a predetermined value. Therefore, according to the airbag 1, the application of undesired pressure on the obstacle 15 can be prevented. The rear panel 3 is made of plural pieces of reinforcing and heat-resisting textile fabrics (base fabrics). The gas outlets 10a may be formed in some of the plural base fabrics constituting the rear panel 3 so that, as the inner pressure in the airbag 1 reaches the predetermined value, the base fabrics not having the outlets so blocking the gas outlets 10a are broken to allow the gas to escape outside. The gas outlets 10a, 10b may be composed of one hole or plural holes, for example, twelve holes, respectively as shown in Fig. 1. In this embodiment, the diameter of the gas outlets 10a, 10b is about 12 mm. The volume of the airbag 1 of this embodiment is 60 liters. The gas outlets 10a and 10b may be positioned around the gas inlet 12b and the inflator insertion opening 12c. Fig. 3 is a partial schematic view of an airbag of an airbag device according to the present invention, this view being taken in a direction from the inside of the airbag toward the rear panel. In the right-hand side of Fig. 3, the illustration of the ring 4 is omitted in order to clarify the characteristics of the rear panel 20. As shown in Fig. 3, cut portions 21 are each formed by cutting a line of a predetermined length extending in a radial direction through the center between adjacent holes 8a. The cut portions 21 are sewn by a seam 22 around the gas inlet 12b. According to the airbag device having the rear panel 20 shown in Fig. 3, gas is spouted from the inflator 6 in the event of a vehicle collision. As gas is spouted from the inflator 6, the airbag is deployed with the pressure of the gas. At this point, as shown in Fig. 2, when the airbag can not fully deployed and the inner pressure of the airbag 1 can not be controlled due to blocking of the vent holes 7, the inner pressure of the airbag 1 is increased. As the inner pressure of the airbag 1 reaches to a predetermined value, the seam 22 of the rear panel 20 is broken so as to form gas outlets. The gas in the airbag 1 escapes outside from the gas outlets of the cut portions 21 so as to prevent the inner pressure of the airbag 1 from exceeding the predetermined value. Therefore, in the airbag device shown in Fig. 3, the application of undesired pressure on the obstacle 15 can be prevented just like the airbag device shown in Fig. 1. A retainer used in the airbag device shown in Fig. 3 may not provided with gas outlets 10b as shown in Fig. 1. The number of the cut portions 21 formed in the rear panel 20 may be arbitrary, instead of four as shown in Fig. 3. The cut portions 21 may be formed in some of the plural base fabrics constituting the rear panel 3 so that, as the inner pressure in the airbag 1 reaches the predetermined value, the residual base fabrics are broken to allow the gas to escape outside. The seam 22 may not be provided or the seam 22 may be composed of one or plural lines. That is, the seam 22 is determined corresponding the pressure of breaking the cut portions 21. To facilitate the breakage of the cut portions 21, the ring may be deformed or a spacer may be provided between the rear panel 20 and the retainer. As the breakage of the cut portions 21 is facilitated by deforming the ring or by the spacer, the breakage of the cut portions 21 can be easily controlled by the seam 22, thereby facilitating the control of the inner pressure of the airbag. Figs. 4(a) and 4(b) show an embodiment of the ring used in the airbag device shown in Fig. 3. Fig. 4(a) is a perspective view of the ring, taken diagonally. The ring 13 has swellings 23 which are formed between holes for screws 9 by pressing. Fig. 4(b) is a front view of the ring 13, in the state where the ring 13 is attached to the rear panel 20 and the retainer 33 and they are laid horizontally. As shown in Fig. 4(b), because of the presence of the swellings 23 of the ring 13, spaces are formed between the ring 13 and the cut portions 21 of the rear panel 20. Therefore, the cut portions 21 are prevented from being clamped between the ring 13 and the retainer 33 so as to allow the easier breakage of the cut portions 21. Fig. 5(a) shows an embodiment of spacers used for the airbag device of the present invention and Fig. 5(b) is a sectional view of the airbag device taken along a line A-A in Fig. 3 with spacers 24 of Fig. 5(a) being applied. The spacers 24 have a predetermined height so that the passages for allowing gas to escape are formed according to this height. Each spacer 24 has a hole 8d corresponding to each screw 9 of the ring 4. As shown in Fig. 5(b), because of the presence of the spacers 24, spaces are formed between the ring 4 and the retainer 33. Therefore, the cut portions 21 are prevented from being clamped between the ring 4 and the retainer 33 so as to allow the easier breakage of the cut portions 21. Gas passes through a space between the ring 4 and the inflator 6 and the spaces (passages) 30 between the ring 4 and the retainer 33 so as to allow the gas to suitably escape, thereby accomplishing smoother deployment of the airbag. The retainer 5 of the airbag device shown in Fig. 1 can be exchanged with the retainer 33 without the gas outlets 10b and, in this case, the spacers 24 may be disposed between the ring 4 and the retainer 33 as shown in Fig. 5(b). In this structure, gas escaping from the gas outlets 10a of the rear panel 3 can escape through the passages 30 between the ring 4 and the retainer 33, thereby exhibiting the same effect. Figs. 6(a), 6(b) show other embodiments of the spacer. A spacer 25 shown in Fig. 6(a) has holes 8d through which the screws 9 of the ring 4 are inserted and convexities 26 around the holes 8d. The spacer 25 are situated between the rear panel 20 and the retainer 33 in the same manner as the spacers 24 shown in Figs. 5(a), 5(b). Therefore, the rear panel 20 is strongly clamped between the ring 4 and the convexities 26 of the spacer 25 so as to form spaces (passages) between the adjacent convexities 26. When the spacer 25 is applied to the airbag device shown in Fig. 3, the cut portions 21 are prevented from being clamped between the ring 4 and the retainer 33 so as to allow the easier breakage of the cut portions 21. Gas passes through the space between the ring 4 and the inflator 6 and the spaces (passages) 30 between the convexities 26 so as to allow the gas to suitably escape, thereby accomplishing smoother deployment of the airbag. Also when the retainer 5 of the airbag device shown in Fig. 1 can be exchanged with the retainer 33 without the gas outlets 10b and the spacer 25 may be disposed between the ring 4 and the retainer 33, the same effect can be obtained. The spacer 27 shown in Fig. 6(b) has holes 8d through which the screws 9 of the ring 4 are inserted and notches 28 formed in portions between the holes 8d. The spacer 27 is disposed between the rear panel 20 and the retainer 33 in the same manner as the spacer 24 shown in Fig. 5(b). When the spacer 27 is applied to the airbag device shown in Fig. 3, as the inner pressure of the airbag 1 reaches a predetermined value, the notches 28 of the spacer 27 are broken by the pressure of gas within the spacer 27. The broken portions 29 thus formed are passages for allowing the gas to escape. Therefore, the inner pressure of the airbag 1 never exceeds the predetermined value so that the application of undesired pressure on the obstacle can be prevented in the same manner as mentioned above. The whole of the spacer 27 may be made of plastics or only the portions including the notches 28 may be made of plastics. This spacer 27 can be applied to an airbag having the gas outlets 10a and the cut portions 21 as shown in Fig. 1 and Fig. 3. The above description was made as regard to the spacers used for the airbag device of the present invention. By using the spacers 24, 25, 27, gas can pass through the space between the ring 4 and the inflator 6 and the spaces (passages) formed by the spacers 24, 25, 27 so as to allow the gas to suitably escape, thereby eliminating the requirement of proving the gas outlet 10a and the cut portions 21 shown in Fig. 1 and Fig. 3. The embodiments of the airbag device of the present invention were described above. In the airbag device of the present invention, the inner pressure of the airbag 1 can be controlled by the gas outlets 10a (Fig. 1), the cut portions 21 (Fig. 3), the passages 30 (Fig. 5), so the vent holes 7 are not necessarily provided. As apparent from the above description, the present invention can provide an airbag device in which the inner pressure of an airbag can be controlled by provision of gas outlets, cut portions, and/or passages so as to provide smooth deployment of the airbag and thus to prevent the application of undesired load regardless of whether an obstacle exists or not.

Claims: An airbag device comprising an airbag (1) having a gas inlet (12b), an inflator (6) for spouting gas into the airbag through the gas inlet (12b), a retainer (5; 33) for fixing said airbag and gas outlets (10a) formed around the gas inlet (12b) for discharging the gas, characterized in that the gas outlets (10a) are composed of cut portions (21) and a seam (22) formed around the gas inlet (12b) wherein said seam (22) is torn to allow the gas to be discharged when the pressure in the airbag (1) reaches a predetermined value. An airbag device as claimed in claim 1, wherein said seam (22) is of a predetermined strength. An airbag devise as claimed in claim 1 or 2, wherein each of the cut portions (21) is formed by cutting a line of predetermined length extending in radial direction from the gas inlet (12b). An airbag device as claimed in any of the claims 1 to 3, wherein a ring (4; 13) is situated inside the airbag (1) around the gas inlet (12b) to hold the airbag (1) between the ring (4; 13) and the retainer (5). An airbag device as claimed in claim 4, wherein a space is formed between said inflator (6) and said ring (4; 13) and a passage (30) is formed between said retainer (5; 33) and said ring (4; 13) so that the gas is discharged through the space and said passage.

Inventors: AMAMORI ICHIRO, FUJII HIROAKI, AMAMORI,ICHIRO, FUJII, HIROAKI, Amamori,Ichiro c/o Takata Corporation, Fujii, Hiroaki c/o Takata Corporation
Applicants: TAKATA CORP, TAKATA CORPORATION
Application year: 1999
Main classification: B60R21
IPC codes: B60R21