Airbag

Abstract: An airbag includes: an upper base cloth (3) having a rear face portion (3c), both side portions (3b,4b) supporting the rear face portion (3c), and an upper face portion (3a); and a lower base cloth (4) having a rear face portion (4c), both side portions (4b) supporting the rear face portion (4c), and a bottom face portion (4a). In the construction, joining portion of the upper base cloth and joining portion of lower base cloth are joined to each other to form a bag-shaped airbag, so that two joining lines (17,18) between the rear face portion of the lower base cloth (4c) and each of the both side portions (4b) of the lower base cloth are smoothly curved in such a manner that middle portions of the two joining lines project towards the occupant, thereby forming a bulging portion at the rear face portion of the lower base cloth (4c).

Description: The present invention relates to an airbag employed in a vehicle such as an automobile, an airplane or the like, and in particular to an airbag which is formed in a 3-dimensional shape and which has a large volume optimal for a front passenger seat of an automobile. In general, an airbag apparatus is structured such that an airbag and an inflator are accommodated in a module equipped in a vehicle interior equipment and the airbag is inflated or expanded inwards of a vehicle compartment by gas ejected from the inflator to protect a vehicle occupant. As examples of vehicle interior equipment, there are a center pad of the steering wheel, an instrument panel, a door trim, a seat and the like. Particularly, regarding an airbag for a front passenger seat, since an instrument panel and an occupant or a passenger are distanced from each other, the airbag is required to have a large volume when it is inflated and to inflate or develop in a 3-dimensional or cubic shape to protect an occupant. As such an airbag for a front passenger seat, there is one which has been disclosed in Japanese Patent Application Laid-Open No.10-315892. This airbag has a base cloth structure comprising three base cloths consisting of a pair of side base cloths and a main base cloth. However, in the airbag comprising three base cloths, there is a drawback that sewing work is complicated and workability is deteriorated due to increase in the number of parts and necessity of 3-dimensional sewing. In view of such a drawback, there has been proposed another one such as shown in Fig. 1 and as disclosed in Japanese Patent Application Laid-Open No. 9-99795. An airbag disclosed in the publication is formed such that two upper and lower base cloths (fabrics) B and C are put one on another and peripheral portions thereof are joined through sewing or the like, it has an advantage in that the number of parts is reduced and workability is improved. In such a conventional airbag A, however, since the upper and lower base cloths B and C are set to the same shape, there is a possibility that, when the airbag A is inflated, a space or gap occurs between the inflated or expanded airbag and the abdomen H1 of a vehicle occupant H. Also, as shown in Fig. 2, there is a possibility that, in a state that the occupant H seats on a front side seat and he/she abuts on the lower base cloth C, the airbag A is pressed by the breast H2 of the occupant H to be displaced in a direction G. JP(A)2000016210 discloses an airbag comprising an upper bag portion and a lower bag portion joined together to form the airbag, the upper bag portion having an upper rear surface and the lower bag portion having a lower rear surface, such that when the airbag is inflated in use the upper rear surface and the lower rear surface together cushion against the upper part of the body of a vehicle occupant. When in use, the upper rear surface extends rearwardly of the lower rear surface which accentuates the problem highlighted above. The present invention has been achieved with such points in mind. The present invention provides an airbag comprising an upper bag portion and a lower bag portion joined together to form an airbag, such that when the airbag is inflated in use the upper bag portion has an upper rear surface which cushions generally against the face of a vehicle occupant and the lower bag portion has a lower rear surface which extends rearwardly of the upper rear surface to cushion generally against an abdomen of said vehicle occupant, wherein the lower bag portion comprises two side portions and the lower rear surface is joined to said side portions at respective joining lines which are each curved in such a manner as to allow the lower rear surface to extend more rearwardly than the upper rear surface when the airbag is inflated during use so that the lower rear surface extends towards the abdomen of said vehicle occupant. Preferably, each of the joining lines comprises an arc-shaped side section and the surface contour of the joining lines changes smoothly. Alternatively, each of the two joining lines comprises a plurality of arc-shaped side sections and the surface contour at the transition between adjacent two arc-shaped side sections having different radius changes smoothly. The embodiment hereinafter described provides an airbag which can protect the abdomen of an occupant securely, whose joining workability is improved owing to structure using a small amount of simple base cloth, and whose manufacturing cost is inexpensively reduced. To achieve the above, the embodiment provides an airbag formed by joining two base cloths constituting an upper piece and a lower piece to form substantially closed box like shape, comprising: an upper base cloth having a first rear face portion opposed to an occupant of a vehicle in an inflated state of the airbag, an upper face portion continuously and substantially perpendicularly disposed with the first rear face portion and two first side portions each connected to the first rear face portion and the upper face portion so that the upper piece is formed in generally box like shape, wherein the upper piece comprises an upper joining line defined between the first rear face portion and the first side portion; and a lower base cloth having a second rear face portion opposed to the occupant in the inflated state of the airbag, a lower face portion continuously and substantially perpendicularly disposed with the second rear face portion and two second side portions each connected to the second rear face portion and the lower face portion so that the lower piece is formed in generally box like shape, wherein the lower piece comprises a lower joining line defined between the second rear face portion and the second side portion, wherein the lower joining lines are smoothly contoured with the middle portion of the joining lines projecting toward the occupant, thereby forming a bulging portion at the second rear face portion. With the embodiment as described, a volume of the lower base cloth abutting on the abdomen of an occupant of a vehicle can be increased, safety to the occupant can be improved. Furthermore, since the airbag is simply structured by two base cloths and it is unnecessary to change the lengths of the joining portions of the upper and lower base cloths, the joining work of the upper and lower base cloths can be performed in the conventional manner so that workability is excellent and manufacturing cost can be reduced. Furthermore, since the budging portion is formed by the arc shape portion or by continuous arcs which are smoothly joined with each other, a surface contour of the bulging portion can be formed smoothly, thereby improving safety. In order that the present invention may be well understood, an embodiment thereof, which is given by way of example only, will now be described with reference to the accompanying drawings, in which: Fig. 1 is a side view showing an inflated state of a conventional airbag; Fig. 2 is a side view showing a state where the airbag shown in Fig. 1 abuts an occupant of a vehicle; Fig. 3 is a perspective view showing an inflated state of an airbag of an embodiment according to the present invention; Figs. 4A and 4B are plan view showing respective base cloths shown in Fig. 3; Fig. 5 is a side view showing an inflated state of the airbag shown in Fig. 3; Fig. 6 is a side view showing a state where the airbag shown in Fig. 5 abuts an occupant of a vehicle; and Fig. 7 is a side view showing a difference between the inflated state of the airbag of the embodiment according to the present invention and the inflated state of the airbag according to the conventional structure. Refering to Figures 3 to 6, an airbag 1 is shown for a front passenger seat equipped in an instrument panel 2 positioned below a front window panel or windshield glass W. This airbag 1 is constituted by two non-coated base cloths (base fabrics) 3 and 4 made from nylon 66 fabric having weight of 200g/m 2 . Shapes of the base cloths 3 and 4 prepared will be explained with reference to Figs. 4A and 4B. In Figs. 4A and 4B, upper sides of the cloths are positioned on a front side of a vehicle and mounted in an instrument panel 2, and lower sides thereof are positioned on a rear side of the vehicle and opposed to an occupant or passenger H of the vehicle. The base cloth 3 is positioned on an upper side, and it is formed generally symmetrically, where generally triangular side portions 3b are formed on both sides of a rectangular upper face portion 3a and a generally semi-circular rear face portion, or surface, 3c is formed on one side of the rear end of the upper face portion 3a. Vent holes 7 for discharging gas after inflation of the airbag are formed at boundary portions between the upper face portion 3a and both side portions 3b. The full width W3 of the base cloth 3 is 1100mm, the full length thereof L3 is 1015mm, and the length of each oblique side 9 is 680mm. The length of a side 8 is 330mm, the length of a side 12 is 550mm, and sides 10 are formed in an arc having a radius of 500mm. The base cloth 4 is positioned on a lower side, and it is formed generally symmetrically, where generally rectangular side portions 4b are formed on both sides of a rectangular bottom face portion 4a, and a generally rectangular rear face portion, or surface, 4c is formed on one side of a rear end of the bottom face portion 4a. A gas introducing hole 5 is formed adjacent to a front end of the bottom face portion 4a and an inflator (not shown) is connected to the gas introducing hole 5 so that gas can be introduced into the airbag. Small holes 6 through which bolts of a retainer (mounting member) for mounting the airbag 1 to a reaction canister are inserted and are formed at a periphery of the gas introducing hole 5. Reinforcing cloth (not shown) is sewn at peripheral portions of the gas introducing hole 5 and small holes 6 so that the peripheral portions are reinforced. The full width W4 of the base cloth 4 is 1100mm, the full length L4 thereof is 1110mm, and the length of each oblique side 14 is 680mm. The length of a side 13 is 330mm, and the length of a side 19 is 550mm. Side sections 15 and 16 constituting the bulging portion 20 are respectively formed by an arc having a radius of 500mm and a side section 17 is formed by an arc having a radius of 100mm. The three arcs of the respective edge portions 15, 16, 17 continue smoothly into each other so that the bulging portion 20 is rounded without abrupt changes in surface contour in the transition between the arcs. This arrangement improves safety when the airbag is inflated and the bulging portion 20 abuts the abdomen of a vehicle occupant. In the base cloths 3 and 4, as shown in Figs. 4A and 4B, the upper face portion 3a and the bottom face portion 4a have the same shape, and a line extending from the side 8 to the slope side 9 and a line extending from the side 9 to the slope side 14 have the same shape, but connection shape between each side portion 3b and the rear face portion 3c and that between each side portion 4b and the rear face portion 4c are different from each other, and correspondingly the shapes of the rear face portions 3c and 4c are different from each other. Next, process for sewing the base cloths 3 and 4 to manufacture the airbag 1 will be explained. In the base cloths 3 and 4, since the full widths W3 and W4 are the same and the lengths and the inclination angles of the slope side 9 are the same as those of the slope side 14, the upper halves of the base cloths 3 and 4 are coincident with each other when the base cloths 3 and 4 are put one on another. The three sides of both the slope sides 9 and 14 and the sides 8 and 13 of the base cloths 3 and 4 are sewn. For example, the sewing work. is performed so as to form stitches of the needle handling number of 3.5/cm using 8 number count yarn of nylon 66 with 21 number count sewing-machine needle. Incidentally, the conditions of the sewing work explained below are the same as this work. Next, when the side 12 and the side 19 are put one on another and are sewn, the base cloths 3 and 4 are respectively formed in a box shape. Next, the joining portions 8, 9 and 12 of the box-shaped base cloth 3 and the joining portions 13, 14 and 19 of the box-shaped base cloth 4 are sewn to form a bag-shaped airbag 1. The side 12a of the base cloth 3 is picked up, and the side 10 and the side 11 are put one on another and they are sewn. Further, after reversion, the side 19a is picked up and the sides 15, 16, 17 and the side 18 are put one on another and they are sewn. Finally, inside and outside are reversed through the gas introducing opening 5 and the sewing work is finished. A joining line J extending along front and rear directions appears on a central portion between the side portions 3b and 4b. Thus, since the airbag with a 3-dimensional shape can be formed by such a simple work that two base cloths 3 and 4 are put one on another and they are sewn, sewing workability can be improved significantly. When the airbag 1 thus formed is inflated as shown in Fig. 5, the volume of the portion of the airbag 1 corresponding to the abdomen H1 of the occupant H is increased, so that the displacement in the G direction can considerably be reduced, as shown in Fig. 6. Fig. 7 shows a comparison of the side shapes of the airbag of the embodiment according to the present invention and the conventional airbag, where, in the portion of the inflated airbag positioned from the joining line J between the side portions 3b and 4b downward by length h (200mm), the length thereof to the rear face portion 3c or 4c is 330 mm in the conventional airbag (L0) and that is 420 mm in the present embodiment (L), so that the distance from the inflated airbag to the abdomen H1 of the occupant H can be reduced as much as 27% in this embodiment. Although the invention has been described above by reference to one embodiment of the invention, the invention is not limited to the embodiment described above. Modifications and variations of the embodiment described above will occur to those skilled in the art, in light of the above teachings. In the above described embodiment, the joining lines between respective lower side portions 4b, 4b and the lower rear surface are each made up of three arc-shaped side sections, in which the transition between the sections is smoothly contoured. However, in a modification, joining lines may be made up of straight lines with arcs therebetween in such a way that the joining lines as a whole are still smoothly contoured. Alternatively, the joining lines may each be made up of a parabola with a continuously varying radius to present a smoothly contoured shape. The scope of the invention is defined with reference to the following claims.

Claims: An airbag comprising an upper bag portion (3) and a lower bag portion (4) joined together to form an airbag (1), such that when the airbag is inflated in use the upper bag portion has an upper rear surface (3c) which cushions generally against the face of a vehicle occupant (H) and the lower bag portion has a lower rear surface (4c) which extends rearwardly of the upper rear surface to cushion generally against an abdomen (H1) of said vehicle occupant, wherein the lower bag portion comprises two side portions (4b, 4b) and the lower rear surface is joined to said side portions (4b, 4b) at respective joining lines which are each curved in such a manner as to allow the lower rear surface to extend more rearwardly than the upper rear surface when the airbag is inflated during use so that the lower rear surface extends towards the abdomen of said vehicle occupant. An airbag as claimed in claim 1, wherein each of the joining lines comprises an arc-shaped side section and the surface contour of the joining lines changes smoothly. An airbag as claimed in claim 1, wherein each of the two joining lines comprises a plurality of arc-shaped side sections 15, 16, 17 and the surface contour at the transition between adjacent two arc-shaped side sections having different radius changes smoothly.

Inventors: WATANABE TSUYOSHI, WATANABE, TSUYOSHI
Applicants: NIHON PLAST CO LTD, NIHON PLAST CO., LTD.
Application year: 2001
Main classification: B60R21
IPC codes: B60R21